<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:b3a67ea9-2582-4e50-9c9e-5a893d56889d,g:7231f70c-41e0-4547-84eb-ed0f9b7b16c7-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://casella.com/role/COVER" xlink:type="simple" xlink:href="cwst-20220930.xsd#COVER"/>
  <link:definitionLink xlink:role="http://casella.com/role/COVER" xlink:type="extended" id="i5b835278434c4537bda4a6644c6d9b81_COVER">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_4fb5ce85-ad49-4352-bbbd-8e1601109adb" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_DocumentType_4fb5ce85-ad49-4352-bbbd-8e1601109adb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_715b56b7-3861-4316-8445-6caee90329ed" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_DocumentQuarterlyReport_715b56b7-3861-4316-8445-6caee90329ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_04415cdf-05fe-42bf-9f19-f8859c7770dd" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_DocumentPeriodEndDate_04415cdf-05fe-42bf-9f19-f8859c7770dd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_499c820c-5781-4d4d-b854-2833175f6315" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_DocumentTransitionReport_499c820c-5781-4d4d-b854-2833175f6315" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_ca35c9f6-34ee-43d6-b971-36b45b260040" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityFileNumber_ca35c9f6-34ee-43d6-b971-36b45b260040" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_6b0405a2-7351-4a2e-925c-5cc211407463" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityRegistrantName_6b0405a2-7351-4a2e-925c-5cc211407463" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_845f4fe9-9fa9-44f2-9713-3438f6cab75b" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityIncorporationStateCountryCode_845f4fe9-9fa9-44f2-9713-3438f6cab75b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_879bfbbb-ab7e-4ad6-bd11-d18a8ed4ee78" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityTaxIdentificationNumber_879bfbbb-ab7e-4ad6-bd11-d18a8ed4ee78" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_55c03546-2cf7-40db-adcb-51da8c0ae98d" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityAddressAddressLine1_55c03546-2cf7-40db-adcb-51da8c0ae98d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_0862738d-56f2-431d-a32e-6d763ba3349f" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityAddressCityOrTown_0862738d-56f2-431d-a32e-6d763ba3349f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_09475bef-287f-4f11-814f-900ffd89f718" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityAddressStateOrProvince_09475bef-287f-4f11-814f-900ffd89f718" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_a0d82020-0cf9-4b15-b490-4f36c638d3f6" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityAddressPostalZipCode_a0d82020-0cf9-4b15-b490-4f36c638d3f6" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_ef104cc6-59ab-47c9-a53f-1c2b321f4d86" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_CityAreaCode_ef104cc6-59ab-47c9-a53f-1c2b321f4d86" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_67f22c6c-f285-4b46-aca4-b7fba320145c" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_LocalPhoneNumber_67f22c6c-f285-4b46-aca4-b7fba320145c" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_2f846be0-0b7d-4796-80f8-aeef259408ee" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_Security12bTitle_2f846be0-0b7d-4796-80f8-aeef259408ee" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_40dd1afa-1ae6-438a-85be-0bc297572cf8" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_TradingSymbol_40dd1afa-1ae6-438a-85be-0bc297572cf8" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_6689b0ed-c1a8-41de-96b7-5e79da402832" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_SecurityExchangeName_6689b0ed-c1a8-41de-96b7-5e79da402832" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_20c9e84c-4d5c-448b-88a0-36bccd1221c6" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityCurrentReportingStatus_20c9e84c-4d5c-448b-88a0-36bccd1221c6" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_ed7778dd-f6d5-43e8-b7f2-c565e9f4cefe" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityInteractiveDataCurrent_ed7778dd-f6d5-43e8-b7f2-c565e9f4cefe" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_9d0d789d-b6dd-4278-8433-7a158d132a3f" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityFilerCategory_9d0d789d-b6dd-4278-8433-7a158d132a3f" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_4c0a3117-0f1f-4927-a86b-d07d6e89ec7c" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntitySmallBusiness_4c0a3117-0f1f-4927-a86b-d07d6e89ec7c" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_2185d01f-3463-45d9-89e8-1d505f6e75dc" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityEmergingGrowthCompany_2185d01f-3463-45d9-89e8-1d505f6e75dc" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_8af30ee0-06fd-49eb-8d39-7db653815e14" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityShellCompany_8af30ee0-06fd-49eb-8d39-7db653815e14" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_0c9833a5-996f-400f-8753-b511517e5120" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_0c9833a5-996f-400f-8753-b511517e5120" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_44f2f545-2712-45da-a89c-e3e3dda5b898" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_EntityCentralIndexKey_44f2f545-2712-45da-a89c-e3e3dda5b898" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_054c6995-a929-41f6-af24-cb8989834964" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_CurrentFiscalYearEndDate_054c6995-a929-41f6-af24-cb8989834964" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_7793e46e-3f4f-44bd-95ac-13234cabcb76" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_DocumentFiscalYearFocus_7793e46e-3f4f-44bd-95ac-13234cabcb76" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_7bcda7b9-c8fd-448d-b4b7-4478b6113ef3" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_DocumentFiscalPeriodFocus_7bcda7b9-c8fd-448d-b4b7-4478b6113ef3" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_0d8cf163-a6ed-437d-a4d2-d22b673b3b8e" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_AmendmentFlag_0d8cf163-a6ed-437d-a4d2-d22b673b3b8e" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_7cc507c1-aa30-4eac-9977-c78550d93986" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_11359d18-bc4f-4a4d-9fed-21c8e979b41c" xlink:to="loc_dei_DocumentInformationTable_7cc507c1-aa30-4eac-9977-c78550d93986" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_108af308-f3ee-4b4f-aa47-655db1a30389" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_7cc507c1-aa30-4eac-9977-c78550d93986" xlink:to="loc_us-gaap_StatementClassOfStockAxis_108af308-f3ee-4b4f-aa47-655db1a30389" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_108af308-f3ee-4b4f-aa47-655db1a30389_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_108af308-f3ee-4b4f-aa47-655db1a30389" xlink:to="loc_us-gaap_ClassOfStockDomain_108af308-f3ee-4b4f-aa47-655db1a30389_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_b560ab4e-f4ed-4beb-a77d-cb33a4b3012f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_108af308-f3ee-4b4f-aa47-655db1a30389" xlink:to="loc_us-gaap_ClassOfStockDomain_b560ab4e-f4ed-4beb-a77d-cb33a4b3012f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_80f06f52-e3ce-40e9-a607-44e3cccbe273" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_b560ab4e-f4ed-4beb-a77d-cb33a4b3012f" xlink:to="loc_us-gaap_CommonClassAMember_80f06f52-e3ce-40e9-a607-44e3cccbe273" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_00de715d-537e-48d5-b098-c86046082952" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_b560ab4e-f4ed-4beb-a77d-cb33a4b3012f" xlink:to="loc_us-gaap_CommonClassBMember_00de715d-537e-48d5-b098-c86046082952" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/CONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="cwst-20220930.xsd#CONSOLIDATEDBALANCESHEETS"/>
  <link:definitionLink xlink:role="http://casella.com/role/CONSOLIDATEDBALANCESHEETS" xlink:type="extended" id="icee5ceddd14242dfb92f7ab98f41464b_CONSOLIDATEDBALANCESHEETS">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_7c88b8ce-dde9-4056-a7a0-4a325743dd15" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_4da97b9e-1f06-483a-8236-afc2ac37f7c4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7c88b8ce-dde9-4056-a7a0-4a325743dd15" xlink:to="loc_us-gaap_AssetsAbstract_4da97b9e-1f06-483a-8236-afc2ac37f7c4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_2f422653-818b-48d4-b7e4-a0f2376f88bb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4da97b9e-1f06-483a-8236-afc2ac37f7c4" xlink:to="loc_us-gaap_AssetsCurrentAbstract_2f422653-818b-48d4-b7e4-a0f2376f88bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_9e0e0cb5-a3f0-4725-bd58-8d5ad2804e63" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_2f422653-818b-48d4-b7e4-a0f2376f88bb" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_9e0e0cb5-a3f0-4725-bd58-8d5ad2804e63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_5efe6451-df4b-423e-b9f8-a4a8980c15bf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_2f422653-818b-48d4-b7e4-a0f2376f88bb" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_5efe6451-df4b-423e-b9f8-a4a8980c15bf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseCurrent_d70e5785-8d22-4321-9b90-fb78e7cab186" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PrepaidExpenseCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_2f422653-818b-48d4-b7e4-a0f2376f88bb" xlink:to="loc_us-gaap_PrepaidExpenseCurrent_d70e5785-8d22-4321-9b90-fb78e7cab186" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryGross_3fc7eca6-9eb9-40fa-8332-ea3a1688f5b1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_2f422653-818b-48d4-b7e4-a0f2376f88bb" xlink:to="loc_us-gaap_InventoryGross_3fc7eca6-9eb9-40fa-8332-ea3a1688f5b1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsCurrent_a934ff77-b7dc-4079-b91e-0ee11d448a97" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_2f422653-818b-48d4-b7e4-a0f2376f88bb" xlink:to="loc_us-gaap_OtherAssetsCurrent_a934ff77-b7dc-4079-b91e-0ee11d448a97" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_734ee98a-51da-4cf2-8184-2a03b57feb09" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_2f422653-818b-48d4-b7e4-a0f2376f88bb" xlink:to="loc_us-gaap_AssetsCurrent_734ee98a-51da-4cf2-8184-2a03b57feb09" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_6d1c1064-4725-4229-a15d-c9b5b7b1f68a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4da97b9e-1f06-483a-8236-afc2ac37f7c4" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_6d1c1064-4725-4229-a15d-c9b5b7b1f68a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_69ed6b48-48de-41dc-b888-6594fbfc1b09" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4da97b9e-1f06-483a-8236-afc2ac37f7c4" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_69ed6b48-48de-41dc-b888-6594fbfc1b09" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_45b1b236-d6ef-4902-8be2-5bbc07027309" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4da97b9e-1f06-483a-8236-afc2ac37f7c4" xlink:to="loc_us-gaap_Goodwill_45b1b236-d6ef-4902-8be2-5bbc07027309" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_e20d44c7-5d06-4754-aaab-4bbbb92eaba2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4da97b9e-1f06-483a-8236-afc2ac37f7c4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_e20d44c7-5d06-4754-aaab-4bbbb92eaba2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndInvestmentsNoncurrent_e77ad2fc-4bc9-4d73-aebc-4632f219f631" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCashAndInvestmentsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4da97b9e-1f06-483a-8236-afc2ac37f7c4" xlink:to="loc_us-gaap_RestrictedCashAndInvestmentsNoncurrent_e77ad2fc-4bc9-4d73-aebc-4632f219f631" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherInvestmentsAndSecuritiesAtCost_2d9298fb-187a-463c-9d40-aaccad3a9dcb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherInvestmentsAndSecuritiesAtCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4da97b9e-1f06-483a-8236-afc2ac37f7c4" xlink:to="loc_us-gaap_OtherInvestmentsAndSecuritiesAtCost_2d9298fb-187a-463c-9d40-aaccad3a9dcb" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_5d7c561a-b4ef-4dee-9ab2-3a8d39ec1a22" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4da97b9e-1f06-483a-8236-afc2ac37f7c4" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_5d7c561a-b4ef-4dee-9ab2-3a8d39ec1a22" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_7adab6c1-133b-4626-b2e9-7c717ecb904a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4da97b9e-1f06-483a-8236-afc2ac37f7c4" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_7adab6c1-133b-4626-b2e9-7c717ecb904a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_3a250224-6945-4e7f-8517-257d9f63e736" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4da97b9e-1f06-483a-8236-afc2ac37f7c4" xlink:to="loc_us-gaap_Assets_3a250224-6945-4e7f-8517-257d9f63e736" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_57818321-9246-4f00-ad85-aa8ce5be8746" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7c88b8ce-dde9-4056-a7a0-4a325743dd15" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_57818321-9246-4f00-ad85-aa8ce5be8746" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_dcf78c07-0ed3-49ae-9101-c1ac17677ead" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_57818321-9246-4f00-ad85-aa8ce5be8746" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_dcf78c07-0ed3-49ae-9101-c1ac17677ead" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent_66778730-3096-4561-9c70-e81687af6819" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_dcf78c07-0ed3-49ae-9101-c1ac17677ead" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent_66778730-3096-4561-9c70-e81687af6819" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_01cc84ee-4195-4ff9-84ed-6de0d5ceedf1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_dcf78c07-0ed3-49ae-9101-c1ac17677ead" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_01cc84ee-4195-4ff9-84ed-6de0d5ceedf1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_ea35f80b-12b8-4e93-aee6-76354b506973" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_dcf78c07-0ed3-49ae-9101-c1ac17677ead" xlink:to="loc_us-gaap_AccountsPayableCurrent_ea35f80b-12b8-4e93-aee6-76354b506973" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_f88b48a4-2849-4b65-a7ec-d6435ba62015" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_dcf78c07-0ed3-49ae-9101-c1ac17677ead" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_f88b48a4-2849-4b65-a7ec-d6435ba62015" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPayableCurrent_5a400141-f087-4ea2-bf6f-945f0e1bc302" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_dcf78c07-0ed3-49ae-9101-c1ac17677ead" xlink:to="loc_us-gaap_InterestPayableCurrent_5a400141-f087-4ea2-bf6f-945f0e1bc302" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_35820104-06db-470e-b605-2dcbbcef3225" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_dcf78c07-0ed3-49ae-9101-c1ac17677ead" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_35820104-06db-470e-b605-2dcbbcef3225" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedCappingClosurePostClosureAndEnvironmentalCosts_49848372-502b-471d-8315-aee536729402" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccruedCappingClosurePostClosureAndEnvironmentalCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_dcf78c07-0ed3-49ae-9101-c1ac17677ead" xlink:to="loc_us-gaap_AccruedCappingClosurePostClosureAndEnvironmentalCosts_49848372-502b-471d-8315-aee536729402" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAccruedLiabilitiesCurrent_ded337f0-baab-469a-a9ac-28cd0be3aa0a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_dcf78c07-0ed3-49ae-9101-c1ac17677ead" xlink:to="loc_us-gaap_OtherAccruedLiabilitiesCurrent_ded337f0-baab-469a-a9ac-28cd0be3aa0a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_45d8b7dc-0a11-4eaa-87b5-9053444e5843" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_dcf78c07-0ed3-49ae-9101-c1ac17677ead" xlink:to="loc_us-gaap_LiabilitiesCurrent_45d8b7dc-0a11-4eaa-87b5-9053444e5843" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_1e2c6aea-c4ce-4af8-be6b-189044d95be0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_57818321-9246-4f00-ad85-aa8ce5be8746" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_1e2c6aea-c4ce-4af8-be6b-189044d95be0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_ddec8fb2-610a-447c-9bb1-2364b538a88c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_57818321-9246-4f00-ad85-aa8ce5be8746" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_ddec8fb2-610a-447c-9bb1-2364b538a88c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedCappingClosurePostClosureAndEnvironmentalCostsNoncurrent_d16eb46c-6801-45a5-9cc6-af0e8c234bad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccruedCappingClosurePostClosureAndEnvironmentalCostsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_57818321-9246-4f00-ad85-aa8ce5be8746" xlink:to="loc_us-gaap_AccruedCappingClosurePostClosureAndEnvironmentalCostsNoncurrent_d16eb46c-6801-45a5-9cc6-af0e8c234bad" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_618d7618-1786-499d-8d0f-e74de1a242dd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_57818321-9246-4f00-ad85-aa8ce5be8746" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_618d7618-1786-499d-8d0f-e74de1a242dd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_a6a9553d-c6a0-463c-be91-6c8dd927cbc7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_57818321-9246-4f00-ad85-aa8ce5be8746" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_a6a9553d-c6a0-463c-be91-6c8dd927cbc7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_9095c2a7-9a26-4744-8dbe-65d99ef3f986" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_57818321-9246-4f00-ad85-aa8ce5be8746" xlink:to="loc_us-gaap_CommitmentsAndContingencies_9095c2a7-9a26-4744-8dbe-65d99ef3f986" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_71f64948-feb2-4209-aeb3-ab9ee2ead04b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_57818321-9246-4f00-ad85-aa8ce5be8746" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_71f64948-feb2-4209-aeb3-ab9ee2ead04b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_2d0bc0d1-fd9f-4ebc-983f-a5e478e2a564" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_71f64948-feb2-4209-aeb3-ab9ee2ead04b" xlink:to="loc_us-gaap_CommonStockValue_2d0bc0d1-fd9f-4ebc-983f-a5e478e2a564" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_d498f96a-19f0-4855-9efa-51d9306fa7a2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_71f64948-feb2-4209-aeb3-ab9ee2ead04b" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_d498f96a-19f0-4855-9efa-51d9306fa7a2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_7e13df70-2980-4068-a6b2-49e911d5371d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_71f64948-feb2-4209-aeb3-ab9ee2ead04b" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_7e13df70-2980-4068-a6b2-49e911d5371d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_e8e54575-dad9-45f2-9ad9-12eeb64620fb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_71f64948-feb2-4209-aeb3-ab9ee2ead04b" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_e8e54575-dad9-45f2-9ad9-12eeb64620fb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_a66b121c-b1a9-4fdc-9c77-c0dc8d4f01a7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_71f64948-feb2-4209-aeb3-ab9ee2ead04b" xlink:to="loc_us-gaap_StockholdersEquity_a66b121c-b1a9-4fdc-9c77-c0dc8d4f01a7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_1d475ae9-e939-492a-9697-570c37fff5b6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_57818321-9246-4f00-ad85-aa8ce5be8746" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_1d475ae9-e939-492a-9697-570c37fff5b6" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_2b4a3a18-ba9b-47af-a609-997eec1b0b89" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_7c88b8ce-dde9-4056-a7a0-4a325743dd15" xlink:to="loc_us-gaap_StatementTable_2b4a3a18-ba9b-47af-a609-997eec1b0b89" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_72495204-88d7-400e-b3e9-0769bb11e0c7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_2b4a3a18-ba9b-47af-a609-997eec1b0b89" xlink:to="loc_us-gaap_StatementClassOfStockAxis_72495204-88d7-400e-b3e9-0769bb11e0c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_72495204-88d7-400e-b3e9-0769bb11e0c7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_72495204-88d7-400e-b3e9-0769bb11e0c7" xlink:to="loc_us-gaap_ClassOfStockDomain_72495204-88d7-400e-b3e9-0769bb11e0c7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_eb82caab-7e18-4698-960b-69a03c663e53" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_72495204-88d7-400e-b3e9-0769bb11e0c7" xlink:to="loc_us-gaap_ClassOfStockDomain_eb82caab-7e18-4698-960b-69a03c663e53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_2186028e-20c2-444a-b232-a8a90320ce75" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_eb82caab-7e18-4698-960b-69a03c663e53" xlink:to="loc_us-gaap_CommonClassAMember_2186028e-20c2-444a-b232-a8a90320ce75" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_723f7ba2-f8ce-48ab-94b6-37bb43f586df" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_eb82caab-7e18-4698-960b-69a03c663e53" xlink:to="loc_us-gaap_CommonClassBMember_723f7ba2-f8ce-48ab-94b6-37bb43f586df" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/CONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="simple" xlink:href="cwst-20220930.xsd#CONSOLIDATEDBALANCESHEETSParenthetical"/>
  <link:definitionLink xlink:role="http://casella.com/role/CONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="extended" id="i810924d180974342adac8c1a0a0f0dfe_CONSOLIDATEDBALANCESHEETSParenthetical">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_1e3614d0-019d-4b0c-a40d-31dfcb676710" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_9336a818-a9a6-48ea-834a-b15e8e9c3226" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1e3614d0-019d-4b0c-a40d-31dfcb676710" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_9336a818-a9a6-48ea-834a-b15e8e9c3226" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_9417d071-c0e1-407c-b981-83f25468a73c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1e3614d0-019d-4b0c-a40d-31dfcb676710" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_9417d071-c0e1-407c-b981-83f25468a73c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_5d5da8c5-5597-4d02-8455-5e89af8ac612" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1e3614d0-019d-4b0c-a40d-31dfcb676710" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_5d5da8c5-5597-4d02-8455-5e89af8ac612" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_f09e8d28-9a78-4553-9f72-a9b27357583e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1e3614d0-019d-4b0c-a40d-31dfcb676710" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_f09e8d28-9a78-4553-9f72-a9b27357583e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_268864d3-13ef-4b49-8636-e156b7f63538" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1e3614d0-019d-4b0c-a40d-31dfcb676710" xlink:to="loc_us-gaap_CommonStockSharesIssued_268864d3-13ef-4b49-8636-e156b7f63538" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_2bd0d8a0-1c2d-49ae-ae2b-bce1a722b720" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1e3614d0-019d-4b0c-a40d-31dfcb676710" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_2bd0d8a0-1c2d-49ae-ae2b-bce1a722b720" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_StockholdersEquityNumberOfVotesEachShare_f4617198-a099-44d4-8707-c8c69cca2d85" xlink:href="cwst-20220930.xsd#cwst_StockholdersEquityNumberOfVotesEachShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1e3614d0-019d-4b0c-a40d-31dfcb676710" xlink:to="loc_cwst_StockholdersEquityNumberOfVotesEachShare_f4617198-a099-44d4-8707-c8c69cca2d85" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_1140e234-50a4-49cb-8d84-ee02a94dc09a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1e3614d0-019d-4b0c-a40d-31dfcb676710" xlink:to="loc_us-gaap_StatementTable_1140e234-50a4-49cb-8d84-ee02a94dc09a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_bc531c93-cb7b-45b1-a093-9c14db33933c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1140e234-50a4-49cb-8d84-ee02a94dc09a" xlink:to="loc_us-gaap_StatementClassOfStockAxis_bc531c93-cb7b-45b1-a093-9c14db33933c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_bc531c93-cb7b-45b1-a093-9c14db33933c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_bc531c93-cb7b-45b1-a093-9c14db33933c" xlink:to="loc_us-gaap_ClassOfStockDomain_bc531c93-cb7b-45b1-a093-9c14db33933c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_d335366e-8357-4602-bb7d-7a0a691c418d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_bc531c93-cb7b-45b1-a093-9c14db33933c" xlink:to="loc_us-gaap_ClassOfStockDomain_d335366e-8357-4602-bb7d-7a0a691c418d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_6d1b3d2c-db81-443c-aa0a-2b0adb97d7ff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_d335366e-8357-4602-bb7d-7a0a691c418d" xlink:to="loc_us-gaap_CommonClassAMember_6d1b3d2c-db81-443c-aa0a-2b0adb97d7ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_983d79fc-11f6-40ff-ab9c-b9b80a466380" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_d335366e-8357-4602-bb7d-7a0a691c418d" xlink:to="loc_us-gaap_CommonClassBMember_983d79fc-11f6-40ff-ab9c-b9b80a466380" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/UNAUDITEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="simple" xlink:href="cwst-20220930.xsd#UNAUDITEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY"/>
  <link:definitionLink xlink:role="http://casella.com/role/UNAUDITEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="extended" id="i4046195ce6d947639c1a33e20406e287_UNAUDITEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_555416b5-e2e3-4507-871c-5c2595ad64b7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_b793769e-e882-4712-9317-0cd33a2b50d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_555416b5-e2e3-4507-871c-5c2595ad64b7" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_b793769e-e882-4712-9317-0cd33a2b50d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_db417b5b-a2f8-4fda-8d44-5c445a74f8cd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_b793769e-e882-4712-9317-0cd33a2b50d6" xlink:to="loc_us-gaap_StockholdersEquity_db417b5b-a2f8-4fda-8d44-5c445a74f8cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_2b54152d-1b8d-4034-a275-e453b8018853" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_b793769e-e882-4712-9317-0cd33a2b50d6" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_2b54152d-1b8d-4034-a275-e453b8018853" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_608940e1-3704-48da-9f35-0b0f143a6ff3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_b793769e-e882-4712-9317-0cd33a2b50d6" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_608940e1-3704-48da-9f35-0b0f143a6ff3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_1c9c3936-6b81-4770-96f8-5ceb01360955" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_b793769e-e882-4712-9317-0cd33a2b50d6" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_1c9c3936-6b81-4770-96f8-5ceb01360955" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_4a2b1200-8152-4661-8d49-3c1a836c3de7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_b793769e-e882-4712-9317-0cd33a2b50d6" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_4a2b1200-8152-4661-8d49-3c1a836c3de7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_bf497ee0-22b5-4a89-8beb-29f36e86bd3d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_b793769e-e882-4712-9317-0cd33a2b50d6" xlink:to="loc_us-gaap_NetIncomeLoss_bf497ee0-22b5-4a89-8beb-29f36e86bd3d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_022f4d90-be1e-4d04-b9ce-e3140a6264a4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_b793769e-e882-4712-9317-0cd33a2b50d6" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_022f4d90-be1e-4d04-b9ce-e3140a6264a4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_7c5ee3e6-2193-4c3c-a018-33509c98af4b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_79d04e70-4414-4d01-9bd6-5bf1a003c401" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_830b4b34-054c-4317-b191-3bc85cb4223d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_555416b5-e2e3-4507-871c-5c2595ad64b7" xlink:to="loc_us-gaap_StatementTable_830b4b34-054c-4317-b191-3bc85cb4223d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_f7d2d33b-00eb-4ddc-beb4-702c58264e27" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_830b4b34-054c-4317-b191-3bc85cb4223d" xlink:to="loc_us-gaap_StatementClassOfStockAxis_f7d2d33b-00eb-4ddc-beb4-702c58264e27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_f7d2d33b-00eb-4ddc-beb4-702c58264e27_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f7d2d33b-00eb-4ddc-beb4-702c58264e27" xlink:to="loc_us-gaap_ClassOfStockDomain_f7d2d33b-00eb-4ddc-beb4-702c58264e27_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_9433e725-be7b-41d9-bf98-9771eaad658c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f7d2d33b-00eb-4ddc-beb4-702c58264e27" xlink:to="loc_us-gaap_ClassOfStockDomain_9433e725-be7b-41d9-bf98-9771eaad658c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_57cd830b-a06f-4d30-92ce-dbf9f254fc7b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_9433e725-be7b-41d9-bf98-9771eaad658c" xlink:to="loc_us-gaap_CommonClassAMember_57cd830b-a06f-4d30-92ce-dbf9f254fc7b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_e959a194-9ee8-4698-81c6-03ddae8019ef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_9433e725-be7b-41d9-bf98-9771eaad658c" xlink:to="loc_us-gaap_CommonClassBMember_e959a194-9ee8-4698-81c6-03ddae8019ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_305287ac-1f3c-477e-8040-b7a34768abe8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_830b4b34-054c-4317-b191-3bc85cb4223d" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_305287ac-1f3c-477e-8040-b7a34768abe8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_305287ac-1f3c-477e-8040-b7a34768abe8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_305287ac-1f3c-477e-8040-b7a34768abe8" xlink:to="loc_us-gaap_EquityComponentDomain_305287ac-1f3c-477e-8040-b7a34768abe8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_ecebcd3c-2b13-4552-a52f-cdf81b9be4df" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_305287ac-1f3c-477e-8040-b7a34768abe8" xlink:to="loc_us-gaap_EquityComponentDomain_ecebcd3c-2b13-4552-a52f-cdf81b9be4df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_c1131dd0-3abe-4755-821f-54d3701be947" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ecebcd3c-2b13-4552-a52f-cdf81b9be4df" xlink:to="loc_us-gaap_CommonStockMember_c1131dd0-3abe-4755-821f-54d3701be947" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_3fc330d8-2e98-4f79-8428-7853de742930" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ecebcd3c-2b13-4552-a52f-cdf81b9be4df" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_3fc330d8-2e98-4f79-8428-7853de742930" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_ffd85fbd-0e8f-44e4-a5b8-e66022a97475" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ecebcd3c-2b13-4552-a52f-cdf81b9be4df" xlink:to="loc_us-gaap_RetainedEarningsMember_ffd85fbd-0e8f-44e4-a5b8-e66022a97475" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_c9a575c4-b093-4f14-a64c-c31ba7c5c6a0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ecebcd3c-2b13-4552-a52f-cdf81b9be4df" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_c9a575c4-b093-4f14-a64c-c31ba7c5c6a0" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/REVENUERECOGNITIONDisaggregationofRevenueDetails" xlink:type="simple" xlink:href="cwst-20220930.xsd#REVENUERECOGNITIONDisaggregationofRevenueDetails"/>
  <link:definitionLink xlink:role="http://casella.com/role/REVENUERECOGNITIONDisaggregationofRevenueDetails" xlink:type="extended" id="i7dc98d1a01964dfe9973506fb5d6615f_REVENUERECOGNITIONDisaggregationofRevenueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_597e4ac0-5cbe-4b93-895d-c7b6a07a4520" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_e9d38a6c-a3c5-4581-a211-aff36bcf4c0e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_597e4ac0-5cbe-4b93-895d-c7b6a07a4520" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_e9d38a6c-a3c5-4581-a211-aff36bcf4c0e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_0e182084-19dd-4016-827e-03e5428e5550" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_597e4ac0-5cbe-4b93-895d-c7b6a07a4520" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_0e182084-19dd-4016-827e-03e5428e5550" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_55ad6d62-8254-4e58-916e-7562eba1840b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_0e182084-19dd-4016-827e-03e5428e5550" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_55ad6d62-8254-4e58-916e-7562eba1840b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_55ad6d62-8254-4e58-916e-7562eba1840b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_55ad6d62-8254-4e58-916e-7562eba1840b" xlink:to="loc_us-gaap_SegmentDomain_55ad6d62-8254-4e58-916e-7562eba1840b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_6aa3e99e-24c4-41f1-af8b-805e1af06299" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_55ad6d62-8254-4e58-916e-7562eba1840b" xlink:to="loc_us-gaap_SegmentDomain_6aa3e99e-24c4-41f1-af8b-805e1af06299" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_EasternRegionMember_c7cadbf0-e6c4-491f-8ddd-4772d327569c" xlink:href="cwst-20220930.xsd#cwst_EasternRegionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_6aa3e99e-24c4-41f1-af8b-805e1af06299" xlink:to="loc_cwst_EasternRegionMember_c7cadbf0-e6c4-491f-8ddd-4772d327569c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_WesternRegionMember_aebd2eee-40bf-43b2-99b7-be7cc8fc0f0c" xlink:href="cwst-20220930.xsd#cwst_WesternRegionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_6aa3e99e-24c4-41f1-af8b-805e1af06299" xlink:to="loc_cwst_WesternRegionMember_aebd2eee-40bf-43b2-99b7-be7cc8fc0f0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_ResourceSolutionsRegionMember_bace3d7d-e656-404e-89d9-56d7d27b0c6c" xlink:href="cwst-20220930.xsd#cwst_ResourceSolutionsRegionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_6aa3e99e-24c4-41f1-af8b-805e1af06299" xlink:to="loc_cwst_ResourceSolutionsRegionMember_bace3d7d-e656-404e-89d9-56d7d27b0c6c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_93d48ca3-8281-44f4-b665-ea339dec487e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TimingOfTransferOfGoodOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_0e182084-19dd-4016-827e-03e5428e5550" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_93d48ca3-8281-44f4-b665-ea339dec487e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_93d48ca3-8281-44f4-b665-ea339dec487e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_93d48ca3-8281-44f4-b665-ea339dec487e" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_93d48ca3-8281-44f4-b665-ea339dec487e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_31932f38-799a-4599-9522-fb2f9068a8e9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_93d48ca3-8281-44f4-b665-ea339dec487e" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_31932f38-799a-4599-9522-fb2f9068a8e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferredAtPointInTimeMember_d0886adb-bb3d-4d19-b3aa-bc3881e869f8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransferredAtPointInTimeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_31932f38-799a-4599-9522-fb2f9068a8e9" xlink:to="loc_us-gaap_TransferredAtPointInTimeMember_d0886adb-bb3d-4d19-b3aa-bc3881e869f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferredOverTimeMember_492b7f4a-dee8-4a23-8577-7bf9784159fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransferredOverTimeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_31932f38-799a-4599-9522-fb2f9068a8e9" xlink:to="loc_us-gaap_TransferredOverTimeMember_492b7f4a-dee8-4a23-8577-7bf9784159fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_294a225c-c906-4c75-8e7b-e5e60cf41f13" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_0e182084-19dd-4016-827e-03e5428e5550" xlink:to="loc_srt_ProductOrServiceAxis_294a225c-c906-4c75-8e7b-e5e60cf41f13" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_294a225c-c906-4c75-8e7b-e5e60cf41f13_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_294a225c-c906-4c75-8e7b-e5e60cf41f13" xlink:to="loc_srt_ProductsAndServicesDomain_294a225c-c906-4c75-8e7b-e5e60cf41f13_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_36934d07-db05-45ad-b01e-410b81eb8d1a" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_294a225c-c906-4c75-8e7b-e5e60cf41f13" xlink:to="loc_srt_ProductsAndServicesDomain_36934d07-db05-45ad-b01e-410b81eb8d1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_CollectionMember_1298bb48-69e1-490f-bae0-6c3172538af5" xlink:href="cwst-20220930.xsd#cwst_CollectionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_36934d07-db05-45ad-b01e-410b81eb8d1a" xlink:to="loc_cwst_CollectionMember_1298bb48-69e1-490f-bae0-6c3172538af5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_LandfillRevenueMember_70707f6c-d767-4ae4-8d27-27329dbbd15a" xlink:href="cwst-20220930.xsd#cwst_LandfillRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_36934d07-db05-45ad-b01e-410b81eb8d1a" xlink:to="loc_cwst_LandfillRevenueMember_70707f6c-d767-4ae4-8d27-27329dbbd15a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_TransferStationMember_b4d29b91-d43b-426b-a8d5-4a7a95c8e729" xlink:href="cwst-20220930.xsd#cwst_TransferStationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_36934d07-db05-45ad-b01e-410b81eb8d1a" xlink:to="loc_cwst_TransferStationMember_b4d29b91-d43b-426b-a8d5-4a7a95c8e729" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_TransportationMember_644942ef-a1e7-4d52-9ecd-2ba6441b4506" xlink:href="cwst-20220930.xsd#cwst_TransportationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_36934d07-db05-45ad-b01e-410b81eb8d1a" xlink:to="loc_cwst_TransportationMember_644942ef-a1e7-4d52-9ecd-2ba6441b4506" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_LandfillGasToEnergyMember_c67d050a-a769-4914-a4e0-2ae78405e6ec" xlink:href="cwst-20220930.xsd#cwst_LandfillGasToEnergyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_36934d07-db05-45ad-b01e-410b81eb8d1a" xlink:to="loc_cwst_LandfillGasToEnergyMember_c67d050a-a769-4914-a4e0-2ae78405e6ec" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_ProcessingServicesMember_db1be09e-a5cd-4fe0-ae73-a44f064af7c9" xlink:href="cwst-20220930.xsd#cwst_ProcessingServicesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_36934d07-db05-45ad-b01e-410b81eb8d1a" xlink:to="loc_cwst_ProcessingServicesMember_db1be09e-a5cd-4fe0-ae73-a44f064af7c9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_NonProcessingServicesMember_c04def61-fe75-46f4-bce9-bc5c937ecdd6" xlink:href="cwst-20220930.xsd#cwst_NonProcessingServicesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_36934d07-db05-45ad-b01e-410b81eb8d1a" xlink:to="loc_cwst_NonProcessingServicesMember_c04def61-fe75-46f4-bce9-bc5c937ecdd6" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/REVENUERECOGNITIONNarrativeDetails" xlink:type="simple" xlink:href="cwst-20220930.xsd#REVENUERECOGNITIONNarrativeDetails"/>
  <link:definitionLink xlink:role="http://casella.com/role/REVENUERECOGNITIONNarrativeDetails" xlink:type="extended" id="i2f9390bdb5e545b68f4a68cbf7a0b16b_REVENUERECOGNITIONNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_b8235b4b-9c1c-463c-b6b5-3fee1abe1bff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_deae905e-722e-48b6-8cd7-b5a2e2e52e91" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_b8235b4b-9c1c-463c-b6b5-3fee1abe1bff" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_deae905e-722e-48b6-8cd7-b5a2e2e52e91" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod_55a76c01-cf4c-429c-85da-ff5cf299feae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_b8235b4b-9c1c-463c-b6b5-3fee1abe1bff" xlink:to="loc_us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod_55a76c01-cf4c-429c-85da-ff5cf299feae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetGrossCurrent_31d031d5-6bdb-47b4-b976-2d5f3b0414b3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerAssetGrossCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_b8235b4b-9c1c-463c-b6b5-3fee1abe1bff" xlink:to="loc_us-gaap_ContractWithCustomerAssetGrossCurrent_31d031d5-6bdb-47b4-b976-2d5f3b0414b3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_3e1077ee-17ef-47a2-871a-a9dd6ac8f91a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_b8235b4b-9c1c-463c-b6b5-3fee1abe1bff" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_3e1077ee-17ef-47a2-871a-a9dd6ac8f91a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_a50da45a-3798-4d0d-a038-be4a8c017583" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_b8235b4b-9c1c-463c-b6b5-3fee1abe1bff" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_a50da45a-3798-4d0d-a038-be4a8c017583" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_e37bf15c-f4bf-4cd6-b9ae-9c46897ce132" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_a50da45a-3798-4d0d-a038-be4a8c017583" xlink:to="loc_srt_ProductOrServiceAxis_e37bf15c-f4bf-4cd6-b9ae-9c46897ce132" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_e37bf15c-f4bf-4cd6-b9ae-9c46897ce132_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_e37bf15c-f4bf-4cd6-b9ae-9c46897ce132" xlink:to="loc_srt_ProductsAndServicesDomain_e37bf15c-f4bf-4cd6-b9ae-9c46897ce132_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_3f882297-dd22-498a-8115-57c9ff885754" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_e37bf15c-f4bf-4cd6-b9ae-9c46897ce132" xlink:to="loc_srt_ProductsAndServicesDomain_3f882297-dd22-498a-8115-57c9ff885754" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_RebateRecycledOrReturnedOrganicMaterialsMember_4383ae2b-565a-4522-9a2a-799437a0a3c6" xlink:href="cwst-20220930.xsd#cwst_RebateRecycledOrReturnedOrganicMaterialsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_3f882297-dd22-498a-8115-57c9ff885754" xlink:to="loc_cwst_RebateRecycledOrReturnedOrganicMaterialsMember_4383ae2b-565a-4522-9a2a-799437a0a3c6" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/BUSINESSCOMBINATIONSNarrativeDetails" xlink:type="simple" xlink:href="cwst-20220930.xsd#BUSINESSCOMBINATIONSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://casella.com/role/BUSINESSCOMBINATIONSNarrativeDetails" xlink:type="extended" id="ie672f439a9284e38be2cc36103cc6a50_BUSINESSCOMBINATIONSNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_e86bd3ad-dc39-467f-8101-51651d09463c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfBusinessesAcquired_32137388-a723-401a-b4ec-8dd38cafbcba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NumberOfBusinessesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_e86bd3ad-dc39-467f-8101-51651d09463c" xlink:to="loc_us-gaap_NumberOfBusinessesAcquired_32137388-a723-401a-b4ec-8dd38cafbcba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_84ad4310-2880-4e22-9ed4-8a0a2f6cd928" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_e86bd3ad-dc39-467f-8101-51651d09463c" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_84ad4310-2880-4e22-9ed4-8a0a2f6cd928" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_b6900a5f-50f3-4a7f-aaa7-6e0866178cff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_e86bd3ad-dc39-467f-8101-51651d09463c" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_b6900a5f-50f3-4a7f-aaa7-6e0866178cff" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_beed8a17-e468-41a1-add6-bbb26c66d41c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_b6900a5f-50f3-4a7f-aaa7-6e0866178cff" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_beed8a17-e468-41a1-add6-bbb26c66d41c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_beed8a17-e468-41a1-add6-bbb26c66d41c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_beed8a17-e468-41a1-add6-bbb26c66d41c" xlink:to="loc_us-gaap_SegmentDomain_beed8a17-e468-41a1-add6-bbb26c66d41c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_5e87a781-31a6-4178-a110-9b04475db21f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_beed8a17-e468-41a1-add6-bbb26c66d41c" xlink:to="loc_us-gaap_SegmentDomain_5e87a781-31a6-4178-a110-9b04475db21f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_WesternRegionMember_0e548411-a5a9-4898-89a6-eb2c2dcfb5d0" xlink:href="cwst-20220930.xsd#cwst_WesternRegionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_5e87a781-31a6-4178-a110-9b04475db21f" xlink:to="loc_cwst_WesternRegionMember_0e548411-a5a9-4898-89a6-eb2c2dcfb5d0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_4f3b9501-b74c-4441-abff-adec3d5f781d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_b6900a5f-50f3-4a7f-aaa7-6e0866178cff" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_4f3b9501-b74c-4441-abff-adec3d5f781d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4f3b9501-b74c-4441-abff-adec3d5f781d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_4f3b9501-b74c-4441-abff-adec3d5f781d" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4f3b9501-b74c-4441-abff-adec3d5f781d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9d0d0462-1150-484c-85a1-96ba8648855d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_4f3b9501-b74c-4441-abff-adec3d5f781d" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9d0d0462-1150-484c-85a1-96ba8648855d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_TuckinSolidWasteCollectionBusinessMember_c7d4b2b1-ac72-406d-8ce5-686aa00819ef" xlink:href="cwst-20220930.xsd#cwst_TuckinSolidWasteCollectionBusinessMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9d0d0462-1150-484c-85a1-96ba8648855d" xlink:to="loc_cwst_TuckinSolidWasteCollectionBusinessMember_c7d4b2b1-ac72-406d-8ce5-686aa00819ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_f90ddc4e-f2a0-4b2e-ada3-62f6f0a01949" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_b6900a5f-50f3-4a7f-aaa7-6e0866178cff" xlink:to="loc_srt_RangeAxis_f90ddc4e-f2a0-4b2e-ada3-62f6f0a01949" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_f90ddc4e-f2a0-4b2e-ada3-62f6f0a01949_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_f90ddc4e-f2a0-4b2e-ada3-62f6f0a01949" xlink:to="loc_srt_RangeMember_f90ddc4e-f2a0-4b2e-ada3-62f6f0a01949_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_d576d432-05b9-475c-ac0e-a3168aba28ec" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_f90ddc4e-f2a0-4b2e-ada3-62f6f0a01949" xlink:to="loc_srt_RangeMember_d576d432-05b9-475c-ac0e-a3168aba28ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_7464a7f0-f2ae-4847-af45-708cff40f426" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_d576d432-05b9-475c-ac0e-a3168aba28ec" xlink:to="loc_srt_MinimumMember_7464a7f0-f2ae-4847-af45-708cff40f426" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_6cc9847f-3c28-464a-b468-bd02b976249e" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_d576d432-05b9-475c-ac0e-a3168aba28ec" xlink:to="loc_srt_MaximumMember_6cc9847f-3c28-464a-b468-bd02b976249e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/BUSINESSCOMBINATIONSSummaryofPurchasePricePaidforAcquisitionsDetail" xlink:type="simple" xlink:href="cwst-20220930.xsd#BUSINESSCOMBINATIONSSummaryofPurchasePricePaidforAcquisitionsDetail"/>
  <link:definitionLink xlink:role="http://casella.com/role/BUSINESSCOMBINATIONSSummaryofPurchasePricePaidforAcquisitionsDetail" xlink:type="extended" id="i1ac25eaf094f449a888b470e3073eee7_BUSINESSCOMBINATIONSSummaryofPurchasePricePaidforAcquisitionsDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_0cbb2667-2fab-4fd0-8850-b11f95a7e764" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_a9f3dd4a-a1c6-4099-9d6f-db2043181216" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationConsiderationTransferredAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_0cbb2667-2fab-4fd0-8850-b11f95a7e764" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_a9f3dd4a-a1c6-4099-9d6f-db2043181216" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_646e7d5b-9d8d-4535-9651-8064970723ba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_a9f3dd4a-a1c6-4099-9d6f-db2043181216" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_646e7d5b-9d8d-4535-9651-8064970723ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredOther1_b6e0c736-56b5-4327-94b6-4910545cd2de" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationConsiderationTransferredOther1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_a9f3dd4a-a1c6-4099-9d6f-db2043181216" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredOther1_b6e0c736-56b5-4327-94b6-4910545cd2de" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_bebd384b-0871-4dce-a0e2-31cdfa61ca88" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_a9f3dd4a-a1c6-4099-9d6f-db2043181216" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_bebd384b-0871-4dce-a0e2-31cdfa61ca88" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_265b74a7-bb9a-4222-9074-21744d676ae8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_a9f3dd4a-a1c6-4099-9d6f-db2043181216" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_265b74a7-bb9a-4222-9074-21744d676ae8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_0cbb2667-2fab-4fd0-8850-b11f95a7e764" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_92c9d2d7-0562-478a-bb41-dba725446406" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_92c9d2d7-0562-478a-bb41-dba725446406" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLand_18a40ee3-02f6-4cb0-aba5-31377ea45e98" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLand"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLand_18a40ee3-02f6-4cb0-aba5-31377ea45e98" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinanceLeaseRightOfUseAsset_b8bc1396-bb24-4ef7-a5e4-0f5c8e96ca34" xlink:href="cwst-20220930.xsd#cwst_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinanceLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:to="loc_cwst_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinanceLeaseRightOfUseAsset_b8bc1396-bb24-4ef7-a5e4-0f5c8e96ca34" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedBuildings_9b4b6cda-82bc-4291-a7c1-c969e07f100f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedBuildings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedBuildings_9b4b6cda-82bc-4291-a7c1-c969e07f100f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedEquipment_cd213b48-ba66-4d1d-b04a-9cffb5792462" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedEquipment_cd213b48-ba66-4d1d-b04a-9cffb5792462" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseRightOfUseAsset_6b42470e-3ab1-4ba3-a028-a995af189ce9" xlink:href="cwst-20220930.xsd#cwst_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:to="loc_cwst_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseRightOfUseAsset_6b42470e-3ab1-4ba3-a028-a995af189ce9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_87f279db-b813-4c77-bfdf-6ac6232f4505" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_87f279db-b813-4c77-bfdf-6ac6232f4505" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_33d9cae0-6fff-4ecf-851d-6344b79979e8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_33d9cae0-6fff-4ecf-851d-6344b79979e8" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_b94a0cca-a60c-40fa-8bb6-f7ba459badf9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_b94a0cca-a60c-40fa-8bb6-f7ba459badf9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_6d8f2cc1-74c6-41d3-bdf6-f1b659ab0700" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_6d8f2cc1-74c6-41d3-bdf6-f1b659ab0700" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinanceLeaseLiabilityNoncurrent_c3c63cdf-6065-485c-8aa5-e888f7c77337" xlink:href="cwst-20220930.xsd#cwst_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinanceLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:to="loc_cwst_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinanceLeaseLiabilityNoncurrent_c3c63cdf-6065-485c-8aa5-e888f7c77337" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseLiabilityNoncurrent_4455db9a-7f31-4088-b812-4aa05fdc83e3" xlink:href="cwst-20220930.xsd#cwst_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:to="loc_cwst_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseLiabilityNoncurrent_4455db9a-7f31-4088-b812-4aa05fdc83e3" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_5c5f845c-c832-4ab9-8323-c55e78f570ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_e8351607-ee88-4188-928f-c5373400a314" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_5c5f845c-c832-4ab9-8323-c55e78f570ec" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_e383cacf-5eee-4cd6-aa2e-b971131a2b93" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_0cbb2667-2fab-4fd0-8850-b11f95a7e764" xlink:to="loc_us-gaap_Goodwill_e383cacf-5eee-4cd6-aa2e-b971131a2b93" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_d460eb3b-7242-40df-bbb6-a225d18cf9b0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_0cbb2667-2fab-4fd0-8850-b11f95a7e764" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_d460eb3b-7242-40df-bbb6-a225d18cf9b0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_628e79aa-0a56-4fac-9e36-406bc9240002" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_d460eb3b-7242-40df-bbb6-a225d18cf9b0" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_628e79aa-0a56-4fac-9e36-406bc9240002" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_628e79aa-0a56-4fac-9e36-406bc9240002_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_628e79aa-0a56-4fac-9e36-406bc9240002" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_628e79aa-0a56-4fac-9e36-406bc9240002_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_dc2af865-a30e-42dd-b788-c427bd1a1817" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_628e79aa-0a56-4fac-9e36-406bc9240002" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_dc2af865-a30e-42dd-b788-c427bd1a1817" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_TransferStationsAcquisitionMember_733180a0-ca21-4635-8030-b14bd13ee89d" xlink:href="cwst-20220930.xsd#cwst_TransferStationsAcquisitionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_dc2af865-a30e-42dd-b788-c427bd1a1817" xlink:to="loc_cwst_TransferStationsAcquisitionMember_733180a0-ca21-4635-8030-b14bd13ee89d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_76b7a101-05ea-443a-9a1b-c952a6e54726" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_d460eb3b-7242-40df-bbb6-a225d18cf9b0" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_76b7a101-05ea-443a-9a1b-c952a6e54726" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_76b7a101-05ea-443a-9a1b-c952a6e54726_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_76b7a101-05ea-443a-9a1b-c952a6e54726" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_76b7a101-05ea-443a-9a1b-c952a6e54726_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8453ca02-e654-418b-b013-ec67ae446601" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_76b7a101-05ea-443a-9a1b-c952a6e54726" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8453ca02-e654-418b-b013-ec67ae446601" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_1e489900-2ee5-44dd-8508-15faef5824f5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8453ca02-e654-418b-b013-ec67ae446601" xlink:to="loc_us-gaap_TradeNamesMember_1e489900-2ee5-44dd-8508-15faef5824f5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_2b3f95cf-c970-452f-926c-2e3100dd94a2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NoncompeteAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8453ca02-e654-418b-b013-ec67ae446601" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_2b3f95cf-c970-452f-926c-2e3100dd94a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_31f53d73-a2d9-4673-82f0-bc80d53b90d5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8453ca02-e654-418b-b013-ec67ae446601" xlink:to="loc_us-gaap_CustomerRelationshipsMember_31f53d73-a2d9-4673-82f0-bc80d53b90d5" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/GOODWILLANDINTANGIBLEASSETSSummaryofGoodwillActivityDetail" xlink:type="simple" xlink:href="cwst-20220930.xsd#GOODWILLANDINTANGIBLEASSETSSummaryofGoodwillActivityDetail"/>
  <link:definitionLink xlink:role="http://casella.com/role/GOODWILLANDINTANGIBLEASSETSSummaryofGoodwillActivityDetail" xlink:type="extended" id="i5daf9f1c0c804e6abc9b12df3115a714_GOODWILLANDINTANGIBLEASSETSSummaryofGoodwillActivityDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_1175ccfa-8b65-4c93-a31d-da91da6356c6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillRollForward_f6e9473a-c195-4104-9df3-f93e908bc948" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GoodwillRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_1175ccfa-8b65-4c93-a31d-da91da6356c6" xlink:to="loc_us-gaap_GoodwillRollForward_f6e9473a-c195-4104-9df3-f93e908bc948" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_1f5e0639-e143-46c0-83c7-71456c4887b8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_f6e9473a-c195-4104-9df3-f93e908bc948" xlink:to="loc_us-gaap_Goodwill_1f5e0639-e143-46c0-83c7-71456c4887b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAcquiredDuringPeriod_8051186e-0739-45eb-90e1-3e71ef8f3eb6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GoodwillAcquiredDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_f6e9473a-c195-4104-9df3-f93e908bc948" xlink:to="loc_us-gaap_GoodwillAcquiredDuringPeriod_8051186e-0739-45eb-90e1-3e71ef8f3eb6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_bb891872-8738-4dce-bae5-db223afa1d98" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GoodwillPurchaseAccountingAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_f6e9473a-c195-4104-9df3-f93e908bc948" xlink:to="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_bb891872-8738-4dce-bae5-db223afa1d98" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_a3cbe023-77c0-4e44-b28d-e8f8e4c857e4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Goodwill"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_1146a29a-94c3-408c-9740-0e349296b3f3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_1175ccfa-8b65-4c93-a31d-da91da6356c6" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_1146a29a-94c3-408c-9740-0e349296b3f3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_416dfcde-739f-4cae-93ba-62e9eb8fbbc6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_1146a29a-94c3-408c-9740-0e349296b3f3" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_416dfcde-739f-4cae-93ba-62e9eb8fbbc6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_416dfcde-739f-4cae-93ba-62e9eb8fbbc6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_416dfcde-739f-4cae-93ba-62e9eb8fbbc6" xlink:to="loc_us-gaap_SegmentDomain_416dfcde-739f-4cae-93ba-62e9eb8fbbc6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_476b3928-0af3-4010-9a03-e975bd99abfc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_416dfcde-739f-4cae-93ba-62e9eb8fbbc6" xlink:to="loc_us-gaap_SegmentDomain_476b3928-0af3-4010-9a03-e975bd99abfc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_EasternRegionMember_bccc4865-fb9e-44f5-b04c-cdbcc40306f5" xlink:href="cwst-20220930.xsd#cwst_EasternRegionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_476b3928-0af3-4010-9a03-e975bd99abfc" xlink:to="loc_cwst_EasternRegionMember_bccc4865-fb9e-44f5-b04c-cdbcc40306f5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_WesternRegionMember_85938107-94b2-411e-acae-9bbffd3cb80a" xlink:href="cwst-20220930.xsd#cwst_WesternRegionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_476b3928-0af3-4010-9a03-e975bd99abfc" xlink:to="loc_cwst_WesternRegionMember_85938107-94b2-411e-acae-9bbffd3cb80a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_ResourceSolutionsRegionMember_e613334a-519f-4032-a5fd-28e20326793e" xlink:href="cwst-20220930.xsd#cwst_ResourceSolutionsRegionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_476b3928-0af3-4010-9a03-e975bd99abfc" xlink:to="loc_cwst_ResourceSolutionsRegionMember_e613334a-519f-4032-a5fd-28e20326793e" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/GOODWILLANDINTANGIBLEASSETSSummaryofIntangibleAssetsbyTypeDetail" xlink:type="simple" xlink:href="cwst-20220930.xsd#GOODWILLANDINTANGIBLEASSETSSummaryofIntangibleAssetsbyTypeDetail"/>
  <link:definitionLink xlink:role="http://casella.com/role/GOODWILLANDINTANGIBLEASSETSSummaryofIntangibleAssetsbyTypeDetail" xlink:type="extended" id="i633a8d7edcf740c9aaa60d781af101aa_GOODWILLANDINTANGIBLEASSETSSummaryofIntangibleAssetsbyTypeDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_3cde6f1c-c8b0-436f-a365-69cf9a953c57" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_c0515e9c-a304-47c8-8ba5-68b4430001bd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_3cde6f1c-c8b0-436f-a365-69cf9a953c57" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_c0515e9c-a304-47c8-8ba5-68b4430001bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_aa386414-26a9-49f6-8938-8c1b13d9e233" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_3cde6f1c-c8b0-436f-a365-69cf9a953c57" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_aa386414-26a9-49f6-8938-8c1b13d9e233" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_8ff31633-9c2c-4162-80c5-02732f632ec9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_3cde6f1c-c8b0-436f-a365-69cf9a953c57" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_8ff31633-9c2c-4162-80c5-02732f632ec9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_fd183acb-fdf6-4c43-802b-b8377cdb400c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_3cde6f1c-c8b0-436f-a365-69cf9a953c57" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_fd183acb-fdf6-4c43-802b-b8377cdb400c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_66b7f285-eb29-4cbf-b7dc-8aebbff7df15" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_fd183acb-fdf6-4c43-802b-b8377cdb400c" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_66b7f285-eb29-4cbf-b7dc-8aebbff7df15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_66b7f285-eb29-4cbf-b7dc-8aebbff7df15_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_66b7f285-eb29-4cbf-b7dc-8aebbff7df15" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_66b7f285-eb29-4cbf-b7dc-8aebbff7df15_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e0113149-3a9c-47f8-98da-8dabc9379f28" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_66b7f285-eb29-4cbf-b7dc-8aebbff7df15" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e0113149-3a9c-47f8-98da-8dabc9379f28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_5ab3d5c1-0063-46d3-8c7b-ff282d5e0914" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NoncompeteAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e0113149-3a9c-47f8-98da-8dabc9379f28" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_5ab3d5c1-0063-46d3-8c7b-ff282d5e0914" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_7a88668a-dbf6-44c1-a87e-bcd371f07d7f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e0113149-3a9c-47f8-98da-8dabc9379f28" xlink:to="loc_us-gaap_CustomerRelationshipsMember_7a88668a-dbf6-44c1-a87e-bcd371f07d7f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_e958fbb9-61f3-42ef-ba80-104fb7814a23" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e0113149-3a9c-47f8-98da-8dabc9379f28" xlink:to="loc_us-gaap_TradeNamesMember_e958fbb9-61f3-42ef-ba80-104fb7814a23" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/DEBTSummaryofDebtDetails" xlink:type="simple" xlink:href="cwst-20220930.xsd#DEBTSummaryofDebtDetails"/>
  <link:definitionLink xlink:role="http://casella.com/role/DEBTSummaryofDebtDetails" xlink:type="extended" id="i20173e203a544b4290d5259dbbf17e85_DEBTSummaryofDebtDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_a1301920-ba88-47ee-8900-8076ae0188a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_51ab99f1-f9f6-4f09-9eda-16a35c9252c2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a1301920-ba88-47ee-8900-8076ae0188a9" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_51ab99f1-f9f6-4f09-9eda-16a35c9252c2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_5fdf9f51-cf72-4779-9a1c-3a74b8d7b464" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a1301920-ba88-47ee-8900-8076ae0188a9" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_5fdf9f51-cf72-4779-9a1c-3a74b8d7b464" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseWeightedAverageDiscountRatePercent_9ff7755c-a573-4389-a3f2-abe40d2670f0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinanceLeaseWeightedAverageDiscountRatePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a1301920-ba88-47ee-8900-8076ae0188a9" xlink:to="loc_us-gaap_FinanceLeaseWeightedAverageDiscountRatePercent_9ff7755c-a573-4389-a3f2-abe40d2670f0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_37639744-8c07-4533-a574-aafa72c7ff97" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a1301920-ba88-47ee-8900-8076ae0188a9" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_37639744-8c07-4533-a574-aafa72c7ff97" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_10493bfb-8a84-4519-b618-e9f8e38f5e42" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a1301920-ba88-47ee-8900-8076ae0188a9" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_10493bfb-8a84-4519-b618-e9f8e38f5e42" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiability_4016b4bf-008d-443c-93bb-097b15c88a4d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinanceLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a1301920-ba88-47ee-8900-8076ae0188a9" xlink:to="loc_us-gaap_FinanceLeaseLiability_4016b4bf-008d-443c-93bb-097b15c88a4d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndCapitalLeaseObligations_c43b5af8-dd3a-4778-9801-37a1e5613152" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a1301920-ba88-47ee-8900-8076ae0188a9" xlink:to="loc_us-gaap_DebtAndCapitalLeaseObligations_c43b5af8-dd3a-4778-9801-37a1e5613152" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_a6483f1c-8a4c-4c09-a4f7-c4df45edbe72" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a1301920-ba88-47ee-8900-8076ae0188a9" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_a6483f1c-8a4c-4c09-a4f7-c4df45edbe72" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities_35029400-f42c-4bbc-b271-790e6b3f7959" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a1301920-ba88-47ee-8900-8076ae0188a9" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities_35029400-f42c-4bbc-b271-790e6b3f7959" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent_f0d92c75-f59c-491a-8ec1-1d1b19487cfa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a1301920-ba88-47ee-8900-8076ae0188a9" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent_f0d92c75-f59c-491a-8ec1-1d1b19487cfa" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_55ad70fe-a8d8-4acf-b9b5-064c4cbbb5c4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a1301920-ba88-47ee-8900-8076ae0188a9" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_55ad70fe-a8d8-4acf-b9b5-064c4cbbb5c4" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityStatementOfFinancialPositionExtensibleList_6f2a2516-3fb2-46d7-98b3-9a4d1371465c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinanceLeaseLiabilityStatementOfFinancialPositionExtensibleList"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a1301920-ba88-47ee-8900-8076ae0188a9" xlink:to="loc_us-gaap_FinanceLeaseLiabilityStatementOfFinancialPositionExtensibleList_6f2a2516-3fb2-46d7-98b3-9a4d1371465c" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_0d2410d8-c868-41f5-8650-0cc198661aa3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a1301920-ba88-47ee-8900-8076ae0188a9" xlink:to="loc_us-gaap_DebtInstrumentTable_0d2410d8-c868-41f5-8650-0cc198661aa3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_1f4af085-81d4-438e-b683-fa9b56f72828" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0d2410d8-c868-41f5-8650-0cc198661aa3" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_1f4af085-81d4-438e-b683-fa9b56f72828" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_1f4af085-81d4-438e-b683-fa9b56f72828_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_1f4af085-81d4-438e-b683-fa9b56f72828" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_1f4af085-81d4-438e-b683-fa9b56f72828_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_9149c7c0-fdd1-4412-b1d2-68f646a8d5e7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_1f4af085-81d4-438e-b683-fa9b56f72828" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_9149c7c0-fdd1-4412-b1d2-68f646a8d5e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_8caefa98-d067-4ed2-ba3f-a53b509bf57e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_9149c7c0-fdd1-4412-b1d2-68f646a8d5e7" xlink:to="loc_us-gaap_SecuredDebtMember_8caefa98-d067-4ed2-ba3f-a53b509bf57e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_cda1ee11-36f8-497d-90cb-5a8bb2402522" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_9149c7c0-fdd1-4412-b1d2-68f646a8d5e7" xlink:to="loc_us-gaap_LineOfCreditMember_cda1ee11-36f8-497d-90cb-5a8bb2402522" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_CreditFacilityMember_60e546c1-5d3e-4249-bad0-03cff3caaf5b" xlink:href="cwst-20220930.xsd#cwst_CreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_9149c7c0-fdd1-4412-b1d2-68f646a8d5e7" xlink:to="loc_cwst_CreditFacilityMember_60e546c1-5d3e-4249-bad0-03cff3caaf5b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_d93269af-a4b3-4e86-a707-35e1a78145c3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_9149c7c0-fdd1-4412-b1d2-68f646a8d5e7" xlink:to="loc_us-gaap_UnsecuredDebtMember_d93269af-a4b3-4e86-a707-35e1a78145c3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_NotesPayableMember_9672e3ac-ba4b-4fdb-a8be-ce9b1c1b7b08" xlink:href="cwst-20220930.xsd#cwst_NotesPayableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_9149c7c0-fdd1-4412-b1d2-68f646a8d5e7" xlink:to="loc_cwst_NotesPayableMember_9672e3ac-ba4b-4fdb-a8be-ce9b1c1b7b08" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_671d1fbd-06f5-4ecb-a25d-34b8fba6b93f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0d2410d8-c868-41f5-8650-0cc198661aa3" xlink:to="loc_us-gaap_DebtInstrumentAxis_671d1fbd-06f5-4ecb-a25d-34b8fba6b93f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_671d1fbd-06f5-4ecb-a25d-34b8fba6b93f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_671d1fbd-06f5-4ecb-a25d-34b8fba6b93f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_671d1fbd-06f5-4ecb-a25d-34b8fba6b93f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_b538211f-433f-4650-9793-296cb0e5cc5a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_671d1fbd-06f5-4ecb-a25d-34b8fba6b93f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_b538211f-433f-4650-9793-296cb0e5cc5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_AmendedTermAFacilityDueDecember2026TermLoanBFacilityMember_8118acd6-288e-45af-869c-e77d9165b714" xlink:href="cwst-20220930.xsd#cwst_AmendedTermAFacilityDueDecember2026TermLoanBFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b538211f-433f-4650-9793-296cb0e5cc5a" xlink:to="loc_cwst_AmendedTermAFacilityDueDecember2026TermLoanBFacilityMember_8118acd6-288e-45af-869c-e77d9165b714" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_RevolvingCreditFacilityDueDecember2026Member_c7af9b51-f21d-4de7-bae8-aaa65281a291" xlink:href="cwst-20220930.xsd#cwst_RevolvingCreditFacilityDueDecember2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b538211f-433f-4650-9793-296cb0e5cc5a" xlink:to="loc_cwst_RevolvingCreditFacilityDueDecember2026Member_c7af9b51-f21d-4de7-bae8-aaa65281a291" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_RevenueBondsSeriesTwoThousandFourteenDueTwoThousandFortyFourMember_5f33992a-6845-4748-9495-4ceee4ac423d" xlink:href="cwst-20220930.xsd#cwst_RevenueBondsSeriesTwoThousandFourteenDueTwoThousandFortyFourMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b538211f-433f-4650-9793-296cb0e5cc5a" xlink:to="loc_cwst_RevenueBondsSeriesTwoThousandFourteenDueTwoThousandFortyFourMember_5f33992a-6845-4748-9495-4ceee4ac423d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_RevenueBondSeriesTwoThousandFourteenRTwoDueTwoThousandFortyFourMember_b78b2bd3-23ee-430e-bbb5-d34a0ef800a2" xlink:href="cwst-20220930.xsd#cwst_RevenueBondSeriesTwoThousandFourteenRTwoDueTwoThousandFortyFourMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b538211f-433f-4650-9793-296cb0e5cc5a" xlink:to="loc_cwst_RevenueBondSeriesTwoThousandFourteenRTwoDueTwoThousandFortyFourMember_b78b2bd3-23ee-430e-bbb5-d34a0ef800a2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_RevenueBondsSeries2020DueSeptember2050Member_1160d138-d409-4b34-aac1-549ca60544e3" xlink:href="cwst-20220930.xsd#cwst_RevenueBondsSeries2020DueSeptember2050Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b538211f-433f-4650-9793-296cb0e5cc5a" xlink:to="loc_cwst_RevenueBondsSeries2020DueSeptember2050Member_1160d138-d409-4b34-aac1-549ca60544e3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_FinanceAuthorityofMaineSolidWasteDisposalRevenueBondsSeries2005R3FAMEBonds2005R3Member_aab962b1-68c1-4ce7-9ab3-ab14f661aef4" xlink:href="cwst-20220930.xsd#cwst_FinanceAuthorityofMaineSolidWasteDisposalRevenueBondsSeries2005R3FAMEBonds2005R3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b538211f-433f-4650-9793-296cb0e5cc5a" xlink:to="loc_cwst_FinanceAuthorityofMaineSolidWasteDisposalRevenueBondsSeries2005R3FAMEBonds2005R3Member_aab962b1-68c1-4ce7-9ab3-ab14f661aef4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_FinanceAuthorityOfMaineSolidWasteDisposalRevenueBondsSeries2015R1Member_3a17efcb-2bbb-4e5c-b07c-e97010f99090" xlink:href="cwst-20220930.xsd#cwst_FinanceAuthorityOfMaineSolidWasteDisposalRevenueBondsSeries2015R1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b538211f-433f-4650-9793-296cb0e5cc5a" xlink:to="loc_cwst_FinanceAuthorityOfMaineSolidWasteDisposalRevenueBondsSeries2015R1Member_3a17efcb-2bbb-4e5c-b07c-e97010f99090" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_FinanceAuthorityOfMaineSolidWasteDisposalRevenueBondsSeries2015R2Member_2864d248-1353-4d12-8f35-8e651f4de1c5" xlink:href="cwst-20220930.xsd#cwst_FinanceAuthorityOfMaineSolidWasteDisposalRevenueBondsSeries2015R2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b538211f-433f-4650-9793-296cb0e5cc5a" xlink:to="loc_cwst_FinanceAuthorityOfMaineSolidWasteDisposalRevenueBondsSeries2015R2Member_2864d248-1353-4d12-8f35-8e651f4de1c5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_LongTermRevenueBondSeriesTwoThousandThirteenDueTwoThousandThirtySixMember_8dffc685-cdf8-4b52-8d4b-f303f7b1964a" xlink:href="cwst-20220930.xsd#cwst_LongTermRevenueBondSeriesTwoThousandThirteenDueTwoThousandThirtySixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b538211f-433f-4650-9793-296cb0e5cc5a" xlink:to="loc_cwst_LongTermRevenueBondSeriesTwoThousandThirteenDueTwoThousandThirtySixMember_8dffc685-cdf8-4b52-8d4b-f303f7b1964a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_LongTermRevenueBondsSeries2022A1DueJune2052Member_cbaabfcc-f54c-482b-89b9-ca7e0a933bab" xlink:href="cwst-20220930.xsd#cwst_LongTermRevenueBondsSeries2022A1DueJune2052Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b538211f-433f-4650-9793-296cb0e5cc5a" xlink:to="loc_cwst_LongTermRevenueBondsSeries2022A1DueJune2052Member_cbaabfcc-f54c-482b-89b9-ca7e0a933bab" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_RevenueBondSeriesTwoThousandThirteenDueTwoThousandTwentyNineMember_85c48e75-fd5d-4fa8-9f24-af32e9be262d" xlink:href="cwst-20220930.xsd#cwst_RevenueBondSeriesTwoThousandThirteenDueTwoThousandTwentyNineMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b538211f-433f-4650-9793-296cb0e5cc5a" xlink:to="loc_cwst_RevenueBondSeriesTwoThousandThirteenDueTwoThousandTwentyNineMember_85c48e75-fd5d-4fa8-9f24-af32e9be262d" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_AmendedRevolvingCreditFacilityAndTermLoanAFacilityMember_5b57d14b-6288-4268-8c3d-fb5d8d1e2c73" xlink:href="cwst-20220930.xsd#cwst_AmendedRevolvingCreditFacilityAndTermLoanAFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b538211f-433f-4650-9793-296cb0e5cc5a" xlink:to="loc_cwst_AmendedRevolvingCreditFacilityAndTermLoanAFacilityMember_5b57d14b-6288-4268-8c3d-fb5d8d1e2c73" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_7ebd65b8-4d21-428d-9fae-2011f875f202" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0d2410d8-c868-41f5-8650-0cc198661aa3" xlink:to="loc_us-gaap_VariableRateAxis_7ebd65b8-4d21-428d-9fae-2011f875f202" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_7ebd65b8-4d21-428d-9fae-2011f875f202_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_7ebd65b8-4d21-428d-9fae-2011f875f202" xlink:to="loc_us-gaap_VariableRateDomain_7ebd65b8-4d21-428d-9fae-2011f875f202_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_6aa41ecb-3894-43aa-9d7c-1443f1be87c3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_7ebd65b8-4d21-428d-9fae-2011f875f202" xlink:to="loc_us-gaap_VariableRateDomain_6aa41ecb-3894-43aa-9d7c-1443f1be87c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_53f5d243-2861-4018-aa5c-7c39a1daf29e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_6aa41ecb-3894-43aa-9d7c-1443f1be87c3" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_53f5d243-2861-4018-aa5c-7c39a1daf29e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/DEBTFinancingActivitiesandCreditFacilityNarrativeDetails" xlink:type="simple" xlink:href="cwst-20220930.xsd#DEBTFinancingActivitiesandCreditFacilityNarrativeDetails"/>
  <link:definitionLink xlink:role="http://casella.com/role/DEBTFinancingActivitiesandCreditFacilityNarrativeDetails" xlink:type="extended" id="i9e12eb8fc5444deca4a6ae8cbaf8b075_DEBTFinancingActivitiesandCreditFacilityNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_b3adb556-a360-42de-8ea8-19508c3b1f56" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_97fed885-ce76-4561-9a50-f4941faa4920" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b3adb556-a360-42de-8ea8-19508c3b1f56" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_97fed885-ce76-4561-9a50-f4941faa4920" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_8188125c-0f9f-4a22-82be-4c54b4991724" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b3adb556-a360-42de-8ea8-19508c3b1f56" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_8188125c-0f9f-4a22-82be-4c54b4991724" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_6c03bdf0-7be0-4997-b291-e27a73d2acef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b3adb556-a360-42de-8ea8-19508c3b1f56" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_6c03bdf0-7be0-4997-b291-e27a73d2acef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_LettersOfCreditSublimit_2f6fb8a6-3817-4259-919c-a6fe8252a16c" xlink:href="cwst-20220930.xsd#cwst_LettersOfCreditSublimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b3adb556-a360-42de-8ea8-19508c3b1f56" xlink:to="loc_cwst_LettersOfCreditSublimit_2f6fb8a6-3817-4259-919c-a6fe8252a16c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_LineOfCreditFacilityAdditionalBorrowingCapacity_81eae4f1-321c-4e4f-89ff-408dae90fdf1" xlink:href="cwst-20220930.xsd#cwst_LineOfCreditFacilityAdditionalBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b3adb556-a360-42de-8ea8-19508c3b1f56" xlink:to="loc_cwst_LineOfCreditFacilityAdditionalBorrowingCapacity_81eae4f1-321c-4e4f-89ff-408dae90fdf1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_b0373b29-0505-4d7d-8c56-9e965dd29e5e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b3adb556-a360-42de-8ea8-19508c3b1f56" xlink:to="loc_us-gaap_DebtInstrumentTerm_b0373b29-0505-4d7d-8c56-9e965dd29e5e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeBasisSpreadOnVariableRate_6bc816ae-ee13-4696-b7a7-7fa971f95c40" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeBasisSpreadOnVariableRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b3adb556-a360-42de-8ea8-19508c3b1f56" xlink:to="loc_us-gaap_DerivativeBasisSpreadOnVariableRate_6bc816ae-ee13-4696-b7a7-7fa971f95c40" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_DebtInstrumentCovenantTermsNetLeverageRatio_ad8b1d00-9363-405a-bf25-a6c671320aaf" xlink:href="cwst-20220930.xsd#cwst_DebtInstrumentCovenantTermsNetLeverageRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b3adb556-a360-42de-8ea8-19508c3b1f56" xlink:to="loc_cwst_DebtInstrumentCovenantTermsNetLeverageRatio_ad8b1d00-9363-405a-bf25-a6c671320aaf" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_219bac48-41fa-417c-aeb8-c644c96f6bed" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b3adb556-a360-42de-8ea8-19508c3b1f56" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_219bac48-41fa-417c-aeb8-c644c96f6bed" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_2631b391-17b8-4029-81f0-2f58da2b2373" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b3adb556-a360-42de-8ea8-19508c3b1f56" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_2631b391-17b8-4029-81f0-2f58da2b2373" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_c368f7d9-c83c-4f8f-87cd-0dc0f8eabaab" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b3adb556-a360-42de-8ea8-19508c3b1f56" xlink:to="loc_us-gaap_LineOfCredit_c368f7d9-c83c-4f8f-87cd-0dc0f8eabaab" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_9775b868-59f8-4573-a088-d96703aa10d9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b3adb556-a360-42de-8ea8-19508c3b1f56" xlink:to="loc_us-gaap_DebtInstrumentTable_9775b868-59f8-4573-a088-d96703aa10d9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_e830ef06-183e-43c1-96c0-947b5c2b9509" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_9775b868-59f8-4573-a088-d96703aa10d9" xlink:to="loc_us-gaap_DebtInstrumentAxis_e830ef06-183e-43c1-96c0-947b5c2b9509" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_e830ef06-183e-43c1-96c0-947b5c2b9509_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_e830ef06-183e-43c1-96c0-947b5c2b9509" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_e830ef06-183e-43c1-96c0-947b5c2b9509_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_7df742b9-af98-4b8e-8eca-381a0e7208b2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_e830ef06-183e-43c1-96c0-947b5c2b9509" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_7df742b9-af98-4b8e-8eca-381a0e7208b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_LongTermRevenueBondsSeries2022A1DueJune2052Member_48a3005b-137f-4be3-9037-77c304a2ed02" xlink:href="cwst-20220930.xsd#cwst_LongTermRevenueBondsSeries2022A1DueJune2052Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_7df742b9-af98-4b8e-8eca-381a0e7208b2" xlink:to="loc_cwst_LongTermRevenueBondsSeries2022A1DueJune2052Member_48a3005b-137f-4be3-9037-77c304a2ed02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_AmendedTermAFacilityDueDecember2026TermLoanBFacilityMember_1aefd2b4-374f-497b-bb6f-d52eb7457ed7" xlink:href="cwst-20220930.xsd#cwst_AmendedTermAFacilityDueDecember2026TermLoanBFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_7df742b9-af98-4b8e-8eca-381a0e7208b2" xlink:to="loc_cwst_AmendedTermAFacilityDueDecember2026TermLoanBFacilityMember_1aefd2b4-374f-497b-bb6f-d52eb7457ed7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_RevolvingCreditFacilityDueDecember2026Member_1f7162dd-4a31-4aaf-bdec-d362cd78937d" xlink:href="cwst-20220930.xsd#cwst_RevolvingCreditFacilityDueDecember2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_7df742b9-af98-4b8e-8eca-381a0e7208b2" xlink:to="loc_cwst_RevolvingCreditFacilityDueDecember2026Member_1f7162dd-4a31-4aaf-bdec-d362cd78937d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_ee2f80a3-8683-4edf-84dc-eb584d35813d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_9775b868-59f8-4573-a088-d96703aa10d9" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_ee2f80a3-8683-4edf-84dc-eb584d35813d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ee2f80a3-8683-4edf-84dc-eb584d35813d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ee2f80a3-8683-4edf-84dc-eb584d35813d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ee2f80a3-8683-4edf-84dc-eb584d35813d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_4f562e68-3696-4c3a-94e5-52c5c5cc479f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ee2f80a3-8683-4edf-84dc-eb584d35813d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_4f562e68-3696-4c3a-94e5-52c5c5cc479f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_8cd892cd-3dec-4441-b654-f250dd793887" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_4f562e68-3696-4c3a-94e5-52c5c5cc479f" xlink:to="loc_us-gaap_UnsecuredDebtMember_8cd892cd-3dec-4441-b654-f250dd793887" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_efeb0f3d-fc86-4b37-9204-1eb7c511db54" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_4f562e68-3696-4c3a-94e5-52c5c5cc479f" xlink:to="loc_us-gaap_SecuredDebtMember_efeb0f3d-fc86-4b37-9204-1eb7c511db54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_22e59e38-cc69-4ac4-8e9f-9b25482691d4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_4f562e68-3696-4c3a-94e5-52c5c5cc479f" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_22e59e38-cc69-4ac4-8e9f-9b25482691d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_8880f7c4-e2b4-4f0b-87a7-42a5e46ce52b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_9775b868-59f8-4573-a088-d96703aa10d9" xlink:to="loc_us-gaap_CreditFacilityAxis_8880f7c4-e2b4-4f0b-87a7-42a5e46ce52b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_8880f7c4-e2b4-4f0b-87a7-42a5e46ce52b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_8880f7c4-e2b4-4f0b-87a7-42a5e46ce52b" xlink:to="loc_us-gaap_CreditFacilityDomain_8880f7c4-e2b4-4f0b-87a7-42a5e46ce52b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_78fe4ae0-445a-4b4e-8967-d84c712faac7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_8880f7c4-e2b4-4f0b-87a7-42a5e46ce52b" xlink:to="loc_us-gaap_CreditFacilityDomain_78fe4ae0-445a-4b4e-8967-d84c712faac7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_838f2853-5333-43ce-b0f3-bd565f79a7c2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_78fe4ae0-445a-4b4e-8967-d84c712faac7" xlink:to="loc_us-gaap_LineOfCreditMember_838f2853-5333-43ce-b0f3-bd565f79a7c2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_dba54b47-5a2e-4f91-8cdc-7856bf62f87a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_78fe4ae0-445a-4b4e-8967-d84c712faac7" xlink:to="loc_us-gaap_LetterOfCreditMember_dba54b47-5a2e-4f91-8cdc-7856bf62f87a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_192a301a-70e4-4d28-b8c8-95e97c83f7c6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_9775b868-59f8-4573-a088-d96703aa10d9" xlink:to="loc_us-gaap_VariableRateAxis_192a301a-70e4-4d28-b8c8-95e97c83f7c6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_192a301a-70e4-4d28-b8c8-95e97c83f7c6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_192a301a-70e4-4d28-b8c8-95e97c83f7c6" xlink:to="loc_us-gaap_VariableRateDomain_192a301a-70e4-4d28-b8c8-95e97c83f7c6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_15848822-ea2d-41a4-9864-bd1076101ac6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_192a301a-70e4-4d28-b8c8-95e97c83f7c6" xlink:to="loc_us-gaap_VariableRateDomain_15848822-ea2d-41a4-9864-bd1076101ac6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_061971cc-3d65-487f-abd7-6fe3b0a26a59" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_15848822-ea2d-41a4-9864-bd1076101ac6" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_061971cc-3d65-487f-abd7-6fe3b0a26a59" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_c6c76d84-5048-4dda-8498-c2b37e1ab47d" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_9775b868-59f8-4573-a088-d96703aa10d9" xlink:to="loc_srt_RangeAxis_c6c76d84-5048-4dda-8498-c2b37e1ab47d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_c6c76d84-5048-4dda-8498-c2b37e1ab47d_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_c6c76d84-5048-4dda-8498-c2b37e1ab47d" xlink:to="loc_srt_RangeMember_c6c76d84-5048-4dda-8498-c2b37e1ab47d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_697ad787-4ac4-4781-a165-24a8bedddcbc" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_c6c76d84-5048-4dda-8498-c2b37e1ab47d" xlink:to="loc_srt_RangeMember_697ad787-4ac4-4781-a165-24a8bedddcbc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_a7ef73a8-d3b6-4c37-be98-d9d6d9774397" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_697ad787-4ac4-4781-a165-24a8bedddcbc" xlink:to="loc_srt_MaximumMember_a7ef73a8-d3b6-4c37-be98-d9d6d9774397" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_faef4f26-4bdb-40e4-bf63-74dcf4d0cdd2" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_697ad787-4ac4-4781-a165-24a8bedddcbc" xlink:to="loc_srt_MinimumMember_faef4f26-4bdb-40e4-bf63-74dcf4d0cdd2" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/DEBTCashFlowHedgesNarrativeDetails" xlink:type="simple" xlink:href="cwst-20220930.xsd#DEBTCashFlowHedgesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://casella.com/role/DEBTCashFlowHedgesNarrativeDetails" xlink:type="extended" id="ib3c3073f1f3640718a99ee4767d46b04_DEBTCashFlowHedgesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_1c6e40c8-f7e8-4da7-938a-160b3dc516ba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_f3d7cead-8d96-4bd4-b0fd-8053c5dff91b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1c6e40c8-f7e8-4da7-938a-160b3dc516ba" xlink:to="loc_us-gaap_DerivativeNotionalAmount_f3d7cead-8d96-4bd4-b0fd-8053c5dff91b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFloorInterestRate_df3603d9-6194-4d0b-9337-f4d9fa36b2b2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeFloorInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1c6e40c8-f7e8-4da7-938a-160b3dc516ba" xlink:to="loc_us-gaap_DerivativeFloorInterestRate_df3603d9-6194-4d0b-9337-f4d9fa36b2b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAverageFixedInterestRate_e3408bf0-b64b-4d65-83f7-698212beafc8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeAverageFixedInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1c6e40c8-f7e8-4da7-938a-160b3dc516ba" xlink:to="loc_us-gaap_DerivativeAverageFixedInterestRate_e3408bf0-b64b-4d65-83f7-698212beafc8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_d6a86cd4-2280-4d5b-88bb-2e938dd914dc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1c6e40c8-f7e8-4da7-938a-160b3dc516ba" xlink:to="loc_us-gaap_DebtInstrumentTable_d6a86cd4-2280-4d5b-88bb-2e938dd914dc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_8212d09b-c0ec-4584-be5e-be4ee98eee95" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d6a86cd4-2280-4d5b-88bb-2e938dd914dc" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_8212d09b-c0ec-4584-be5e-be4ee98eee95" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_8212d09b-c0ec-4584-be5e-be4ee98eee95_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_8212d09b-c0ec-4584-be5e-be4ee98eee95" xlink:to="loc_us-gaap_HedgingRelationshipDomain_8212d09b-c0ec-4584-be5e-be4ee98eee95_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_1ff409fa-d2e2-427d-bf9d-349f9c15458a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_8212d09b-c0ec-4584-be5e-be4ee98eee95" xlink:to="loc_us-gaap_HedgingRelationshipDomain_1ff409fa-d2e2-427d-bf9d-349f9c15458a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_4358821d-2159-4f74-8772-35035b97ce38" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_1ff409fa-d2e2-427d-bf9d-349f9c15458a" xlink:to="loc_us-gaap_CashFlowHedgingMember_4358821d-2159-4f74-8772-35035b97ce38" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_61b977e1-4132-4b9c-9788-463ac589d19f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d6a86cd4-2280-4d5b-88bb-2e938dd914dc" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_61b977e1-4132-4b9c-9788-463ac589d19f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_61b977e1-4132-4b9c-9788-463ac589d19f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_61b977e1-4132-4b9c-9788-463ac589d19f" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_61b977e1-4132-4b9c-9788-463ac589d19f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_012f8fcf-d835-4298-88bb-fa7d5174bc16" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_61b977e1-4132-4b9c-9788-463ac589d19f" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_012f8fcf-d835-4298-88bb-fa7d5174bc16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_c60674d4-d8fc-4f88-8d9f-63846f2d470b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_012f8fcf-d835-4298-88bb-fa7d5174bc16" xlink:to="loc_us-gaap_InterestRateContractMember_c60674d4-d8fc-4f88-8d9f-63846f2d470b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_ForwardInterestRateContractMember_2951188f-7c6b-4bb5-af98-f569c53fa8e9" xlink:href="cwst-20220930.xsd#cwst_ForwardInterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_012f8fcf-d835-4298-88bb-fa7d5174bc16" xlink:to="loc_cwst_ForwardInterestRateContractMember_2951188f-7c6b-4bb5-af98-f569c53fa8e9" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/DEBTSummaryofCashFlowHedgesDetails" xlink:type="simple" xlink:href="cwst-20220930.xsd#DEBTSummaryofCashFlowHedgesDetails"/>
  <link:definitionLink xlink:role="http://casella.com/role/DEBTSummaryofCashFlowHedgesDetails" xlink:type="extended" id="iec9bd556faad440782b96ea73737c078_DEBTSummaryofCashFlowHedgesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_bd755506-b8e8-44ee-9798-7efa2471760d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityFairValueGrossAsset_6eba810f-4747-4bf2-ba5a-b65e615d77ee" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeLiabilityFairValueGrossAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_bd755506-b8e8-44ee-9798-7efa2471760d" xlink:to="loc_us-gaap_DerivativeLiabilityFairValueGrossAsset_6eba810f-4747-4bf2-ba5a-b65e615d77ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_6bec3d64-3c56-4b26-a0fd-e400b9555652" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_bd755506-b8e8-44ee-9798-7efa2471760d" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_6bec3d64-3c56-4b26-a0fd-e400b9555652" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossBeforeTax1_ea5e4222-14e1-4627-8179-32b0c84a3ba5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossBeforeTax1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_bd755506-b8e8-44ee-9798-7efa2471760d" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossBeforeTax1_ea5e4222-14e1-4627-8179-32b0c84a3ba5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestTax_bfe20d27-6e5e-42b4-86ad-cc4132e8ad54" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_bd755506-b8e8-44ee-9798-7efa2471760d" xlink:to="loc_us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestTax_bfe20d27-6e5e-42b4-86ad-cc4132e8ad54" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_6346007b-c31e-4948-a46c-2b9bbb5a15c1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_bd755506-b8e8-44ee-9798-7efa2471760d" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_6346007b-c31e-4948-a46c-2b9bbb5a15c1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_027f7eac-9af8-424a-90b2-f0bc407ec228" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_bd755506-b8e8-44ee-9798-7efa2471760d" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_027f7eac-9af8-424a-90b2-f0bc407ec228" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_7b8a7dcf-cf11-4f68-81d7-80147b1ca8dc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_027f7eac-9af8-424a-90b2-f0bc407ec228" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_7b8a7dcf-cf11-4f68-81d7-80147b1ca8dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_7b8a7dcf-cf11-4f68-81d7-80147b1ca8dc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_7b8a7dcf-cf11-4f68-81d7-80147b1ca8dc" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_7b8a7dcf-cf11-4f68-81d7-80147b1ca8dc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_30da12f4-a2cb-49c9-86ea-b9bb40ddd82b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_7b8a7dcf-cf11-4f68-81d7-80147b1ca8dc" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_30da12f4-a2cb-49c9-86ea-b9bb40ddd82b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCurrentAssetsMember_db133020-3223-4d48-9f93-8ee415cb4c80" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherCurrentAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_30da12f4-a2cb-49c9-86ea-b9bb40ddd82b" xlink:to="loc_us-gaap_OtherCurrentAssetsMember_db133020-3223-4d48-9f93-8ee415cb4c80" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncurrentAssetsMember_a631af25-38a9-4b7f-9c44-eb15855d03ff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherNoncurrentAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_30da12f4-a2cb-49c9-86ea-b9bb40ddd82b" xlink:to="loc_us-gaap_OtherNoncurrentAssetsMember_a631af25-38a9-4b7f-9c44-eb15855d03ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_OtherAccruedLiabilitiesMember_c25c3c17-c1b7-4a75-b505-7e06877b2b74" xlink:href="cwst-20220930.xsd#cwst_OtherAccruedLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_30da12f4-a2cb-49c9-86ea-b9bb40ddd82b" xlink:to="loc_cwst_OtherAccruedLiabilitiesMember_c25c3c17-c1b7-4a75-b505-7e06877b2b74" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncurrentLiabilitiesMember_215bb21d-b74f-44f8-b297-7b6ab628c4ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherNoncurrentLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_30da12f4-a2cb-49c9-86ea-b9bb40ddd82b" xlink:to="loc_us-gaap_OtherNoncurrentLiabilitiesMember_215bb21d-b74f-44f8-b297-7b6ab628c4ec" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_e280579f-37b2-404a-878f-2333ee1e1b42" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_027f7eac-9af8-424a-90b2-f0bc407ec228" xlink:to="loc_us-gaap_HedgingDesignationAxis_e280579f-37b2-404a-878f-2333ee1e1b42" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_e280579f-37b2-404a-878f-2333ee1e1b42_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_e280579f-37b2-404a-878f-2333ee1e1b42" xlink:to="loc_us-gaap_HedgingDesignationDomain_e280579f-37b2-404a-878f-2333ee1e1b42_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_a3944f6e-48b3-47b9-bd8d-c38bb5381dab" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_e280579f-37b2-404a-878f-2333ee1e1b42" xlink:to="loc_us-gaap_HedgingDesignationDomain_a3944f6e-48b3-47b9-bd8d-c38bb5381dab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_7ad57dde-e455-425d-b004-717dcc52854d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_a3944f6e-48b3-47b9-bd8d-c38bb5381dab" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_7ad57dde-e455-425d-b004-717dcc52854d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_b37e10d2-cda0-4f5d-a04e-57be3e3521d7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_027f7eac-9af8-424a-90b2-f0bc407ec228" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_b37e10d2-cda0-4f5d-a04e-57be3e3521d7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_b37e10d2-cda0-4f5d-a04e-57be3e3521d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_b37e10d2-cda0-4f5d-a04e-57be3e3521d7" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_b37e10d2-cda0-4f5d-a04e-57be3e3521d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_2964fdde-598f-4725-ac1f-e6b5743b9efb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_b37e10d2-cda0-4f5d-a04e-57be3e3521d7" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_2964fdde-598f-4725-ac1f-e6b5743b9efb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_f013d616-f7fd-4f81-9041-99d14a4da2ba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_2964fdde-598f-4725-ac1f-e6b5743b9efb" xlink:to="loc_us-gaap_InterestRateSwapMember_f013d616-f7fd-4f81-9041-99d14a4da2ba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_ad33d9cd-c9a9-4053-968a-58725d21a655" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_027f7eac-9af8-424a-90b2-f0bc407ec228" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_ad33d9cd-c9a9-4053-968a-58725d21a655" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_ad33d9cd-c9a9-4053-968a-58725d21a655_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_ad33d9cd-c9a9-4053-968a-58725d21a655" xlink:to="loc_us-gaap_EquityComponentDomain_ad33d9cd-c9a9-4053-968a-58725d21a655_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_d6770c7d-6c05-46df-ae2a-2f1256659a51" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_ad33d9cd-c9a9-4053-968a-58725d21a655" xlink:to="loc_us-gaap_EquityComponentDomain_d6770c7d-6c05-46df-ae2a-2f1256659a51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterestMember_ef6a8844-3e99-4173-9a71-b48e87708e65" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_d6770c7d-6c05-46df-ae2a-2f1256659a51" xlink:to="loc_us-gaap_AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterestMember_ef6a8844-3e99-4173-9a71-b48e87708e65" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/COMMITMENTSANDCONTINGENCIESNarrativeDetail" xlink:type="simple" xlink:href="cwst-20220930.xsd#COMMITMENTSANDCONTINGENCIESNarrativeDetail"/>
  <link:definitionLink xlink:role="http://casella.com/role/COMMITMENTSANDCONTINGENCIESNarrativeDetail" xlink:type="extended" id="i7408c2cc058646559aad0ff3ba8e77bd_COMMITMENTSANDCONTINGENCIESNarrativeDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_ee6a5bf3-4e05-47fc-baab-09e4e2695b70" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_cec05bfd-2d6f-4682-b780-936fe27dba42" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_ee6a5bf3-4e05-47fc-baab-09e4e2695b70" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_cec05bfd-2d6f-4682-b780-936fe27dba42" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingenciesDiscountRate_c3bff4e4-0fad-483a-b0c6-a1a3fb17ad3d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccrualForEnvironmentalLossContingenciesDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_ee6a5bf3-4e05-47fc-baab-09e4e2695b70" xlink:to="loc_us-gaap_AccrualForEnvironmentalLossContingenciesDiscountRate_c3bff4e4-0fad-483a-b0c6-a1a3fb17ad3d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_474e49da-cd58-40bd-a5ec-5aa5ad56fa48" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_ee6a5bf3-4e05-47fc-baab-09e4e2695b70" xlink:to="loc_us-gaap_LossContingenciesTable_474e49da-cd58-40bd-a5ec-5aa5ad56fa48" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_b2b6fdb8-ce32-4b17-bd9b-7b811795b78b" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_474e49da-cd58-40bd-a5ec-5aa5ad56fa48" xlink:to="loc_srt_RangeAxis_b2b6fdb8-ce32-4b17-bd9b-7b811795b78b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_b2b6fdb8-ce32-4b17-bd9b-7b811795b78b_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_b2b6fdb8-ce32-4b17-bd9b-7b811795b78b" xlink:to="loc_srt_RangeMember_b2b6fdb8-ce32-4b17-bd9b-7b811795b78b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_8c7a3a51-8513-4107-805c-2887e0382c2c" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_b2b6fdb8-ce32-4b17-bd9b-7b811795b78b" xlink:to="loc_srt_RangeMember_8c7a3a51-8513-4107-805c-2887e0382c2c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_1042dc44-5802-4b19-b5f8-6a2d23ace806" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_8c7a3a51-8513-4107-805c-2887e0382c2c" xlink:to="loc_srt_MinimumMember_1042dc44-5802-4b19-b5f8-6a2d23ace806" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_2afc5055-4280-48ce-b572-3e4ac7a2dc80" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_8c7a3a51-8513-4107-805c-2887e0382c2c" xlink:to="loc_srt_MaximumMember_2afc5055-4280-48ce-b572-3e4ac7a2dc80" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/COMMITMENTSANDCONTINGENCIESEnvironmentalRemediationLiabilityDetails" xlink:type="simple" xlink:href="cwst-20220930.xsd#COMMITMENTSANDCONTINGENCIESEnvironmentalRemediationLiabilityDetails"/>
  <link:definitionLink xlink:role="http://casella.com/role/COMMITMENTSANDCONTINGENCIESEnvironmentalRemediationLiabilityDetails" xlink:type="extended" id="i0de6008334ad42daac8f05bf7f16d2db_COMMITMENTSANDCONTINGENCIESEnvironmentalRemediationLiabilityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SiteContingencyLineItems_32bed028-cb9f-451f-9931-3ba059229755" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SiteContingencyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingenciesRollForward_f95d778c-b449-41ba-8a83-edf7c670f591" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccrualForEnvironmentalLossContingenciesRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SiteContingencyLineItems_32bed028-cb9f-451f-9931-3ba059229755" xlink:to="loc_us-gaap_AccrualForEnvironmentalLossContingenciesRollForward_f95d778c-b449-41ba-8a83-edf7c670f591" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingencies_d55109f5-42ab-4a24-b561-795cf04b3dde" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccrualForEnvironmentalLossContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccrualForEnvironmentalLossContingenciesRollForward_f95d778c-b449-41ba-8a83-edf7c670f591" xlink:to="loc_us-gaap_AccrualForEnvironmentalLossContingencies_d55109f5-42ab-4a24-b561-795cf04b3dde" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses_0b84b5e4-f3d4-4965-84bd-81c086ec81d3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccrualForEnvironmentalLossContingenciesRollForward_f95d778c-b449-41ba-8a83-edf7c670f591" xlink:to="loc_us-gaap_AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses_0b84b5e4-f3d4-4965-84bd-81c086ec81d3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingenciesPayments1_d1a1f9fa-b9de-49eb-b9db-b2e1bb179039" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccrualForEnvironmentalLossContingenciesPayments1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccrualForEnvironmentalLossContingenciesRollForward_f95d778c-b449-41ba-8a83-edf7c670f591" xlink:to="loc_us-gaap_AccrualForEnvironmentalLossContingenciesPayments1_d1a1f9fa-b9de-49eb-b9db-b2e1bb179039" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingencies_ee699139-0a85-4417-b699-6d8bc664fb81" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccrualForEnvironmentalLossContingencies"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedEnvironmentalLossContingenciesCurrent_6e58749c-4aba-42db-9e4f-77a1f695ca6b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccruedEnvironmentalLossContingenciesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SiteContingencyLineItems_32bed028-cb9f-451f-9931-3ba059229755" xlink:to="loc_us-gaap_AccruedEnvironmentalLossContingenciesCurrent_6e58749c-4aba-42db-9e4f-77a1f695ca6b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedEnvironmentalLossContingenciesNoncurrent_1f7b7fcf-ead3-43f8-be17-d28c03789e2a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccruedEnvironmentalLossContingenciesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SiteContingencyLineItems_32bed028-cb9f-451f-9931-3ba059229755" xlink:to="loc_us-gaap_AccruedEnvironmentalLossContingenciesNoncurrent_1f7b7fcf-ead3-43f8-be17-d28c03789e2a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SiteContingencyTable_f395cabf-78b4-4264-8afa-f9ecae3ecd96" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SiteContingencyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SiteContingencyLineItems_32bed028-cb9f-451f-9931-3ba059229755" xlink:to="loc_us-gaap_SiteContingencyTable_f395cabf-78b4-4264-8afa-f9ecae3ecd96" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EnvironmentalRemediationSiteAxis_f8035a55-e8a7-46e0-9c20-3fef462b5d94" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EnvironmentalRemediationSiteAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SiteContingencyTable_f395cabf-78b4-4264-8afa-f9ecae3ecd96" xlink:to="loc_us-gaap_EnvironmentalRemediationSiteAxis_f8035a55-e8a7-46e0-9c20-3fef462b5d94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EnvironmentalRemediationSiteDomain_f8035a55-e8a7-46e0-9c20-3fef462b5d94_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EnvironmentalRemediationSiteDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_EnvironmentalRemediationSiteAxis_f8035a55-e8a7-46e0-9c20-3fef462b5d94" xlink:to="loc_us-gaap_EnvironmentalRemediationSiteDomain_f8035a55-e8a7-46e0-9c20-3fef462b5d94_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EnvironmentalRemediationSiteDomain_17d0e5bd-550a-44cf-8a9b-3acae51038ab" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EnvironmentalRemediationSiteDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_EnvironmentalRemediationSiteAxis_f8035a55-e8a7-46e0-9c20-3fef462b5d94" xlink:to="loc_us-gaap_EnvironmentalRemediationSiteDomain_17d0e5bd-550a-44cf-8a9b-3acae51038ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_EnvironmentalRemediationContingencyOtherMember_c6515c8e-7b99-4923-be0b-553630f22e44" xlink:href="cwst-20220930.xsd#cwst_EnvironmentalRemediationContingencyOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EnvironmentalRemediationSiteDomain_17d0e5bd-550a-44cf-8a9b-3acae51038ab" xlink:to="loc_cwst_EnvironmentalRemediationContingencyOtherMember_c6515c8e-7b99-4923-be0b-553630f22e44" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_InactiveWasteDisposalSiteMember_07aa549e-ec4e-4f4c-9c7e-b20d74eb5786" xlink:href="cwst-20220930.xsd#cwst_InactiveWasteDisposalSiteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EnvironmentalRemediationSiteDomain_17d0e5bd-550a-44cf-8a9b-3acae51038ab" xlink:to="loc_cwst_InactiveWasteDisposalSiteMember_07aa549e-ec4e-4f4c-9c7e-b20d74eb5786" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/STOCKHOLDERSEQUITYNarrativeDetail" xlink:type="simple" xlink:href="cwst-20220930.xsd#STOCKHOLDERSEQUITYNarrativeDetail"/>
  <link:definitionLink xlink:role="http://casella.com/role/STOCKHOLDERSEQUITYNarrativeDetail" xlink:type="extended" id="i3e630ee38e9748ac80d89280b349bbfe_STOCKHOLDERSEQUITYNarrativeDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_528f766d-2047-4c49-8c16-d2db09e8314c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LimitedPartnersCapitalAccountLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_dc173569-32bb-4553-b5cc-7852f5595190" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_528f766d-2047-4c49-8c16-d2db09e8314c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_dc173569-32bb-4553-b5cc-7852f5595190" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_7b5819e6-e2e4-4756-ac8a-2921e4dbb124" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_528f766d-2047-4c49-8c16-d2db09e8314c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_7b5819e6-e2e4-4756-ac8a-2921e4dbb124" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_20ea37cc-b279-4406-a123-51850ee2d90d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_528f766d-2047-4c49-8c16-d2db09e8314c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_20ea37cc-b279-4406-a123-51850ee2d90d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_46f61bbb-b63a-4b6d-abd7-75d61c2e440e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_528f766d-2047-4c49-8c16-d2db09e8314c" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_46f61bbb-b63a-4b6d-abd7-75d61c2e440e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_40488452-6285-4de5-95bb-53c55971b3a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_528f766d-2047-4c49-8c16-d2db09e8314c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_40488452-6285-4de5-95bb-53c55971b3a9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_5499057d-1e57-433c-a01f-f3609995a1bc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_528f766d-2047-4c49-8c16-d2db09e8314c" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_5499057d-1e57-433c-a01f-f3609995a1bc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_ee893161-f48a-4dbc-bf16-91357d526a7a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_528f766d-2047-4c49-8c16-d2db09e8314c" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_ee893161-f48a-4dbc-bf16-91357d526a7a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_e454bd93-b964-48f3-a156-07e5202fd785" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_528f766d-2047-4c49-8c16-d2db09e8314c" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_e454bd93-b964-48f3-a156-07e5202fd785" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_b6846c23-a612-4208-8485-1332e4f751a6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_528f766d-2047-4c49-8c16-d2db09e8314c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_b6846c23-a612-4208-8485-1332e4f751a6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1_3b562714-d7c1-4037-86e9-62030b0c792b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_528f766d-2047-4c49-8c16-d2db09e8314c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1_3b562714-d7c1-4037-86e9-62030b0c792b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_c5cca4ea-08b0-4db8-b90d-cc55c6ab0f10" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_528f766d-2047-4c49-8c16-d2db09e8314c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_c5cca4ea-08b0-4db8-b90d-cc55c6ab0f10" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_2839bc58-999d-44f9-9be4-4cc6c381828e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_528f766d-2047-4c49-8c16-d2db09e8314c" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_2839bc58-999d-44f9-9be4-4cc6c381828e" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_b0234067-7057-4948-a1c5-d596f39e4d59" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_528f766d-2047-4c49-8c16-d2db09e8314c" xlink:to="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_b0234067-7057-4948-a1c5-d596f39e4d59" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_cdb19a23-a38c-439e-a24d-a58109e44582" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_b0234067-7057-4948-a1c5-d596f39e4d59" xlink:to="loc_us-gaap_StatementClassOfStockAxis_cdb19a23-a38c-439e-a24d-a58109e44582" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_cdb19a23-a38c-439e-a24d-a58109e44582_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_cdb19a23-a38c-439e-a24d-a58109e44582" xlink:to="loc_us-gaap_ClassOfStockDomain_cdb19a23-a38c-439e-a24d-a58109e44582_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_fcc657b8-7257-4393-a6f2-677decd86879" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_cdb19a23-a38c-439e-a24d-a58109e44582" xlink:to="loc_us-gaap_ClassOfStockDomain_fcc657b8-7257-4393-a6f2-677decd86879" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_23f8543d-9813-4e16-b75a-3ca4ae0f9083" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_fcc657b8-7257-4393-a6f2-677decd86879" xlink:to="loc_us-gaap_CommonClassAMember_23f8543d-9813-4e16-b75a-3ca4ae0f9083" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_db9b5c7d-d672-45c5-9faf-7b870ffd0828" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_b0234067-7057-4948-a1c5-d596f39e4d59" xlink:to="loc_us-gaap_PlanNameAxis_db9b5c7d-d672-45c5-9faf-7b870ffd0828" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_db9b5c7d-d672-45c5-9faf-7b870ffd0828_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_db9b5c7d-d672-45c5-9faf-7b870ffd0828" xlink:to="loc_us-gaap_PlanNameDomain_db9b5c7d-d672-45c5-9faf-7b870ffd0828_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_da981ee1-d647-43a6-b66b-a426db2815ef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_db9b5c7d-d672-45c5-9faf-7b870ffd0828" xlink:to="loc_us-gaap_PlanNameDomain_da981ee1-d647-43a6-b66b-a426db2815ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_A2016IncentivePlanMember_1117aa74-e4de-4749-9755-fd4ca28d72e6" xlink:href="cwst-20220930.xsd#cwst_A2016IncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_da981ee1-d647-43a6-b66b-a426db2815ef" xlink:to="loc_cwst_A2016IncentivePlanMember_1117aa74-e4de-4749-9755-fd4ca28d72e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_TwoThousandSixStockIncentivePlanMember_b7a1a149-2665-45ad-a0f4-21e58e1caca1" xlink:href="cwst-20220930.xsd#cwst_TwoThousandSixStockIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_da981ee1-d647-43a6-b66b-a426db2815ef" xlink:to="loc_cwst_TwoThousandSixStockIncentivePlanMember_b7a1a149-2665-45ad-a0f4-21e58e1caca1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_AmendedAndRestatedNineteenNinetySevenEmployeeStockPurchasePlanMember_3b8f1e97-4290-44b0-a775-4d66b393f1d0" xlink:href="cwst-20220930.xsd#cwst_AmendedAndRestatedNineteenNinetySevenEmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_da981ee1-d647-43a6-b66b-a426db2815ef" xlink:to="loc_cwst_AmendedAndRestatedNineteenNinetySevenEmployeeStockPurchasePlanMember_3b8f1e97-4290-44b0-a775-4d66b393f1d0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_8c7fbc48-0d9c-4820-a493-527c68c9ecbc" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_b0234067-7057-4948-a1c5-d596f39e4d59" xlink:to="loc_srt_RangeAxis_8c7fbc48-0d9c-4820-a493-527c68c9ecbc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_8c7fbc48-0d9c-4820-a493-527c68c9ecbc_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_8c7fbc48-0d9c-4820-a493-527c68c9ecbc" xlink:to="loc_srt_RangeMember_8c7fbc48-0d9c-4820-a493-527c68c9ecbc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_f7da4530-665e-48de-b3fa-af11895e0aa4" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_8c7fbc48-0d9c-4820-a493-527c68c9ecbc" xlink:to="loc_srt_RangeMember_f7da4530-665e-48de-b3fa-af11895e0aa4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_73aa1cd2-3ce8-452c-8f62-eda871917a2a" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f7da4530-665e-48de-b3fa-af11895e0aa4" xlink:to="loc_srt_MinimumMember_73aa1cd2-3ce8-452c-8f62-eda871917a2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_b38ba94a-6603-4078-aa77-99c0bfd8450d" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f7da4530-665e-48de-b3fa-af11895e0aa4" xlink:to="loc_srt_MaximumMember_b38ba94a-6603-4078-aa77-99c0bfd8450d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_WeightedAverageMember_083e37c3-ea81-47ee-b22d-9d75d84a0efb" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_WeightedAverageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f7da4530-665e-48de-b3fa-af11895e0aa4" xlink:to="loc_srt_WeightedAverageMember_083e37c3-ea81-47ee-b22d-9d75d84a0efb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_994d5e2b-32b4-41ac-9b15-5a0fb3c4cdec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_b0234067-7057-4948-a1c5-d596f39e4d59" xlink:to="loc_us-gaap_AwardTypeAxis_994d5e2b-32b4-41ac-9b15-5a0fb3c4cdec" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_994d5e2b-32b4-41ac-9b15-5a0fb3c4cdec_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_994d5e2b-32b4-41ac-9b15-5a0fb3c4cdec" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_994d5e2b-32b4-41ac-9b15-5a0fb3c4cdec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1217d402-a8d9-4023-819c-fa4ff22b2890" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_994d5e2b-32b4-41ac-9b15-5a0fb3c4cdec" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1217d402-a8d9-4023-819c-fa4ff22b2890" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_f24b1f29-403e-497c-9ec8-a0627c3f2db4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1217d402-a8d9-4023-819c-fa4ff22b2890" xlink:to="loc_us-gaap_EmployeeStockOptionMember_f24b1f29-403e-497c-9ec8-a0627c3f2db4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_RestrictedStockRestrictedStockUnitsAndPerformanceStockUnitsMember_11d79035-2dcd-4137-a77e-62e763030278" xlink:href="cwst-20220930.xsd#cwst_RestrictedStockRestrictedStockUnitsAndPerformanceStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1217d402-a8d9-4023-819c-fa4ff22b2890" xlink:to="loc_cwst_RestrictedStockRestrictedStockUnitsAndPerformanceStockUnitsMember_11d79035-2dcd-4137-a77e-62e763030278" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_RestrictedStockAwardsMember_91757a7a-d53b-41fb-8456-f1aac10471ea" xlink:href="cwst-20220930.xsd#cwst_RestrictedStockAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cwst_RestrictedStockRestrictedStockUnitsAndPerformanceStockUnitsMember_11d79035-2dcd-4137-a77e-62e763030278" xlink:to="loc_cwst_RestrictedStockAwardsMember_91757a7a-d53b-41fb-8456-f1aac10471ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_43742e60-17d9-4cd6-8519-d140df74089b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cwst_RestrictedStockRestrictedStockUnitsAndPerformanceStockUnitsMember_11d79035-2dcd-4137-a77e-62e763030278" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_43742e60-17d9-4cd6-8519-d140df74089b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_PerformanceStockUnitMember_3cd6211d-5524-4f46-934c-9205f81b860d" xlink:href="cwst-20220930.xsd#cwst_PerformanceStockUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cwst_RestrictedStockRestrictedStockUnitsAndPerformanceStockUnitsMember_11d79035-2dcd-4137-a77e-62e763030278" xlink:to="loc_cwst_PerformanceStockUnitMember_3cd6211d-5524-4f46-934c-9205f81b860d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualAxis_c95b30cd-16ed-46b7-90b5-6e8dabf7db2a" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_TitleOfIndividualAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_b0234067-7057-4948-a1c5-d596f39e4d59" xlink:to="loc_srt_TitleOfIndividualAxis_c95b30cd-16ed-46b7-90b5-6e8dabf7db2a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_c95b30cd-16ed-46b7-90b5-6e8dabf7db2a_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_c95b30cd-16ed-46b7-90b5-6e8dabf7db2a" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_c95b30cd-16ed-46b7-90b5-6e8dabf7db2a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_e0a70653-5e3e-4547-b278-629a7cc78127" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_c95b30cd-16ed-46b7-90b5-6e8dabf7db2a" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_e0a70653-5e3e-4547-b278-629a7cc78127" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_NonEmployeeDirectorMember_00e552a5-33b5-4fd5-b2ef-6cec12f44424" xlink:href="cwst-20220930.xsd#cwst_NonEmployeeDirectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_e0a70653-5e3e-4547-b278-629a7cc78127" xlink:to="loc_cwst_NonEmployeeDirectorMember_00e552a5-33b5-4fd5-b2ef-6cec12f44424" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/STOCKHOLDERSEQUITYSummaryofRestrictedStockAwardsRestrictedStockUnitandPerformancebasedStockUnitActivityDetail" xlink:type="simple" xlink:href="cwst-20220930.xsd#STOCKHOLDERSEQUITYSummaryofRestrictedStockAwardsRestrictedStockUnitandPerformancebasedStockUnitActivityDetail"/>
  <link:definitionLink xlink:role="http://casella.com/role/STOCKHOLDERSEQUITYSummaryofRestrictedStockAwardsRestrictedStockUnitandPerformancebasedStockUnitActivityDetail" xlink:type="extended" id="id688e67f695d4a5aad0858f734b1f041_STOCKHOLDERSEQUITYSummaryofRestrictedStockAwardsRestrictedStockUnitandPerformancebasedStockUnitActivityDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_722aed12-2c3b-4880-9e5e-a6900211bc87" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_608ab241-a1fe-4d4e-b553-b2c0c8116668" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_722aed12-2c3b-4880-9e5e-a6900211bc87" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_608ab241-a1fe-4d4e-b553-b2c0c8116668" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_1c2e16bf-aa8b-4d75-9ec8-c9d70952357f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_608ab241-a1fe-4d4e-b553-b2c0c8116668" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_1c2e16bf-aa8b-4d75-9ec8-c9d70952357f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_9685963b-eaa5-4f12-b29b-9484234318dc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_608ab241-a1fe-4d4e-b553-b2c0c8116668" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_9685963b-eaa5-4f12-b29b-9484234318dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_344e71cf-e56d-4a13-94ad-0ed37df315da" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_608ab241-a1fe-4d4e-b553-b2c0c8116668" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_344e71cf-e56d-4a13-94ad-0ed37df315da" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_22ff15fe-4c7d-4554-9b1d-de0f9eac3906" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_608ab241-a1fe-4d4e-b553-b2c0c8116668" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_22ff15fe-4c7d-4554-9b1d-de0f9eac3906" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_eedcab7b-357d-4faa-8927-704aac3e8e6a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_99afd0b9-9291-4944-9083-a4c9641c7cab" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_722aed12-2c3b-4880-9e5e-a6900211bc87" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_99afd0b9-9291-4944-9083-a4c9641c7cab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_9a1438fc-77b4-4a24-a3f3-e8b0147c19ce" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_99afd0b9-9291-4944-9083-a4c9641c7cab" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_9a1438fc-77b4-4a24-a3f3-e8b0147c19ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_bc112701-3576-42a3-9535-8bf4dabd5e31" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_99afd0b9-9291-4944-9083-a4c9641c7cab" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_bc112701-3576-42a3-9535-8bf4dabd5e31" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_87bdba05-81a5-45fc-b23b-773487cd1a4f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_99afd0b9-9291-4944-9083-a4c9641c7cab" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_87bdba05-81a5-45fc-b23b-773487cd1a4f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_fe90ad05-da79-4b8e-8f94-a279b07b0b81" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_99afd0b9-9291-4944-9083-a4c9641c7cab" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_fe90ad05-da79-4b8e-8f94-a279b07b0b81" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_762ccbc7-ac04-43a7-baf2-8170083f7ffa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_6fc79f7a-c9bb-4306-a1dd-edc6cebecd4f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_722aed12-2c3b-4880-9e5e-a6900211bc87" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_6fc79f7a-c9bb-4306-a1dd-edc6cebecd4f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms_aca7cc8a-26b4-4267-b9b9-54157523d3fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_6fc79f7a-c9bb-4306-a1dd-edc6cebecd4f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms_aca7cc8a-26b4-4267-b9b9-54157523d3fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding_517c9f14-e255-483c-8b9f-adb68adfe8e2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_6fc79f7a-c9bb-4306-a1dd-edc6cebecd4f" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding_517c9f14-e255-483c-8b9f-adb68adfe8e2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_799e9af1-2f4e-49e0-be16-2a3ec3cef10f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_722aed12-2c3b-4880-9e5e-a6900211bc87" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_799e9af1-2f4e-49e0-be16-2a3ec3cef10f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_AdditionalSharesIssuedMaximumAttainmentLevel_4791c398-5bb5-4710-ab2d-c0e9b16b7d9b" xlink:href="cwst-20220930.xsd#cwst_AdditionalSharesIssuedMaximumAttainmentLevel"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_722aed12-2c3b-4880-9e5e-a6900211bc87" xlink:to="loc_cwst_AdditionalSharesIssuedMaximumAttainmentLevel_4791c398-5bb5-4710-ab2d-c0e9b16b7d9b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_cfb159f0-f76c-4f37-b278-7c740122a544" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_722aed12-2c3b-4880-9e5e-a6900211bc87" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_cfb159f0-f76c-4f37-b278-7c740122a544" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_b9802c9d-fdb7-4c92-9428-7a266cd61687" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VestingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_cfb159f0-f76c-4f37-b278-7c740122a544" xlink:to="loc_us-gaap_VestingAxis_b9802c9d-fdb7-4c92-9428-7a266cd61687" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_b9802c9d-fdb7-4c92-9428-7a266cd61687_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_b9802c9d-fdb7-4c92-9428-7a266cd61687" xlink:to="loc_us-gaap_VestingDomain_b9802c9d-fdb7-4c92-9428-7a266cd61687_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_a67d8852-5a13-4374-860b-f77dcb2f4073" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_b9802c9d-fdb7-4c92-9428-7a266cd61687" xlink:to="loc_us-gaap_VestingDomain_a67d8852-5a13-4374-860b-f77dcb2f4073" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_601e378b-18ef-4972-8160-3822fbfcdc5d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationAwardTrancheOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_a67d8852-5a13-4374-860b-f77dcb2f4073" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_601e378b-18ef-4972-8160-3822fbfcdc5d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_1fb4491f-34aa-4778-b9dd-9bd363f9f79a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_cfb159f0-f76c-4f37-b278-7c740122a544" xlink:to="loc_us-gaap_AwardTypeAxis_1fb4491f-34aa-4778-b9dd-9bd363f9f79a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1fb4491f-34aa-4778-b9dd-9bd363f9f79a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_1fb4491f-34aa-4778-b9dd-9bd363f9f79a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1fb4491f-34aa-4778-b9dd-9bd363f9f79a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_54aee346-d6ee-4951-8f22-b6ff070b56d1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_1fb4491f-34aa-4778-b9dd-9bd363f9f79a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_54aee346-d6ee-4951-8f22-b6ff070b56d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_PerformanceStockUnitMember_874402e3-e0bc-4b4b-bb03-70e9b3000080" xlink:href="cwst-20220930.xsd#cwst_PerformanceStockUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_54aee346-d6ee-4951-8f22-b6ff070b56d1" xlink:to="loc_cwst_PerformanceStockUnitMember_874402e3-e0bc-4b4b-bb03-70e9b3000080" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_RestrictedStockRestrictedStockUnitsAndPerformanceStockUnitsMember_7e69530a-8933-4aa4-aaf7-4cc6acd93b04" xlink:href="cwst-20220930.xsd#cwst_RestrictedStockRestrictedStockUnitsAndPerformanceStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cwst_PerformanceStockUnitMember_874402e3-e0bc-4b4b-bb03-70e9b3000080" xlink:to="loc_cwst_RestrictedStockRestrictedStockUnitsAndPerformanceStockUnitsMember_7e69530a-8933-4aa4-aaf7-4cc6acd93b04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_61088e11-efb5-432e-a475-d95a522be9c0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_cfb159f0-f76c-4f37-b278-7c740122a544" xlink:to="loc_us-gaap_StatementClassOfStockAxis_61088e11-efb5-432e-a475-d95a522be9c0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_61088e11-efb5-432e-a475-d95a522be9c0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_61088e11-efb5-432e-a475-d95a522be9c0" xlink:to="loc_us-gaap_ClassOfStockDomain_61088e11-efb5-432e-a475-d95a522be9c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_310cb503-6efa-43a2-afa2-6c4aa63017ae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_61088e11-efb5-432e-a475-d95a522be9c0" xlink:to="loc_us-gaap_ClassOfStockDomain_310cb503-6efa-43a2-afa2-6c4aa63017ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_8c7d864b-3365-4f65-ab1d-99d94a4ed4f0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_310cb503-6efa-43a2-afa2-6c4aa63017ae" xlink:to="loc_us-gaap_CommonClassAMember_8c7d864b-3365-4f65-ab1d-99d94a4ed4f0" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/STOCKHOLDERSEQUITYSummaryofChangesinBalancesofEachComponentofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="simple" xlink:href="cwst-20220930.xsd#STOCKHOLDERSEQUITYSummaryofChangesinBalancesofEachComponentofAccumulatedOtherComprehensiveIncomeDetails"/>
  <link:definitionLink xlink:role="http://casella.com/role/STOCKHOLDERSEQUITYSummaryofChangesinBalancesofEachComponentofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="extended" id="i64eee3522b774d2f814b5be6e582ed5c_STOCKHOLDERSEQUITYSummaryofChangesinBalancesofEachComponentofAccumulatedOtherComprehensiveIncomeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_d3eb6792-d9c0-4a09-98a1-be2217382154" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_fdd0460f-ec88-44b4-b8e1-084121e6adc3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_d3eb6792-d9c0-4a09-98a1-be2217382154" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_fdd0460f-ec88-44b4-b8e1-084121e6adc3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_e851a436-31bb-43dd-889d-c54d3335c5f7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_fdd0460f-ec88-44b4-b8e1-084121e6adc3" xlink:to="loc_us-gaap_StockholdersEquity_e851a436-31bb-43dd-889d-c54d3335c5f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_6a88a877-f61e-451e-96d6-c5a374d7d2ac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_fdd0460f-ec88-44b4-b8e1-084121e6adc3" xlink:to="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_6a88a877-f61e-451e-96d6-c5a374d7d2ac" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_0fe95818-20c5-4312-8540-00ec3e1a46d3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_fdd0460f-ec88-44b4-b8e1-084121e6adc3" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_0fe95818-20c5-4312-8540-00ec3e1a46d3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTax_67ea7b94-c718-4019-a7fe-5219c2e49dec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_fdd0460f-ec88-44b4-b8e1-084121e6adc3" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTax_67ea7b94-c718-4019-a7fe-5219c2e49dec" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_5b36ec07-61cb-4b6d-9fc1-3018db642c3f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_fdd0460f-ec88-44b4-b8e1-084121e6adc3" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_5b36ec07-61cb-4b6d-9fc1-3018db642c3f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_63791e67-c839-40de-95c2-316056681263" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_f8ad74de-6d95-4497-a07a-5dbbc34c815d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_d3eb6792-d9c0-4a09-98a1-be2217382154" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_f8ad74de-6d95-4497-a07a-5dbbc34c815d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_d78e6fd1-eeb5-4ee7-a3b7-95da130f1c5c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_f8ad74de-6d95-4497-a07a-5dbbc34c815d" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_d78e6fd1-eeb5-4ee7-a3b7-95da130f1c5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_d78e6fd1-eeb5-4ee7-a3b7-95da130f1c5c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_d78e6fd1-eeb5-4ee7-a3b7-95da130f1c5c" xlink:to="loc_us-gaap_EquityComponentDomain_d78e6fd1-eeb5-4ee7-a3b7-95da130f1c5c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_0964dede-d5e4-4861-a84e-2f71704b39ed" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_d78e6fd1-eeb5-4ee7-a3b7-95da130f1c5c" xlink:to="loc_us-gaap_EquityComponentDomain_0964dede-d5e4-4861-a84e-2f71704b39ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_be906ca0-1ef9-4dc9-ae22-46a3a94844a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_0964dede-d5e4-4861-a84e-2f71704b39ed" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_be906ca0-1ef9-4dc9-ae22-46a3a94844a9" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/STOCKHOLDERSEQUITYSummaryofReclassificationsOutofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="simple" xlink:href="cwst-20220930.xsd#STOCKHOLDERSEQUITYSummaryofReclassificationsOutofAccumulatedOtherComprehensiveIncomeDetails"/>
  <link:definitionLink xlink:role="http://casella.com/role/STOCKHOLDERSEQUITYSummaryofReclassificationsOutofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="extended" id="i4497fd52739645c38adf11815f17a804_STOCKHOLDERSEQUITYSummaryofReclassificationsOutofAccumulatedOtherComprehensiveIncomeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_c66c939a-f86c-4a61-9a2d-0020b4d699bb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_d6ae243a-5b56-4c95-abad-1f72e8f9ab8a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_c66c939a-f86c-4a61-9a2d-0020b4d699bb" xlink:to="loc_us-gaap_InterestExpense_d6ae243a-5b56-4c95-abad-1f72e8f9ab8a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_cbc0320c-fea7-41cd-a23e-36bb4366fa00" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_c66c939a-f86c-4a61-9a2d-0020b4d699bb" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_cbc0320c-fea7-41cd-a23e-36bb4366fa00" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_698a2c21-09d3-4d60-a115-7d9c85c85a7a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_c66c939a-f86c-4a61-9a2d-0020b4d699bb" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_698a2c21-09d3-4d60-a115-7d9c85c85a7a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_7c5b0b8f-b322-42e5-ba86-52d9f12e4ed7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_c66c939a-f86c-4a61-9a2d-0020b4d699bb" xlink:to="loc_us-gaap_NetIncomeLoss_7c5b0b8f-b322-42e5-ba86-52d9f12e4ed7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_bbf310b2-dd44-4a8e-9cbf-200fc8898390" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_c66c939a-f86c-4a61-9a2d-0020b4d699bb" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_bbf310b2-dd44-4a8e-9cbf-200fc8898390" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_0d0f7976-6ab4-4164-8288-b3cd7cf1139f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_bbf310b2-dd44-4a8e-9cbf-200fc8898390" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_0d0f7976-6ab4-4164-8288-b3cd7cf1139f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_0d0f7976-6ab4-4164-8288-b3cd7cf1139f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_0d0f7976-6ab4-4164-8288-b3cd7cf1139f" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_0d0f7976-6ab4-4164-8288-b3cd7cf1139f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_094a7d90-4488-4a9d-aad4-b41e4c830c71" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_0d0f7976-6ab4-4164-8288-b3cd7cf1139f" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_094a7d90-4488-4a9d-aad4-b41e4c830c71" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_fbdc7cd9-41b8-4c2a-9bf5-d3d09d02326d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_094a7d90-4488-4a9d-aad4-b41e4c830c71" xlink:to="loc_us-gaap_InterestRateSwapMember_fbdc7cd9-41b8-4c2a-9bf5-d3d09d02326d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_aa386a80-5bef-41cd-8c69-051c7f0602fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_bbf310b2-dd44-4a8e-9cbf-200fc8898390" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_aa386a80-5bef-41cd-8c69-051c7f0602fa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_aa386a80-5bef-41cd-8c69-051c7f0602fa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_aa386a80-5bef-41cd-8c69-051c7f0602fa" xlink:to="loc_us-gaap_EquityComponentDomain_aa386a80-5bef-41cd-8c69-051c7f0602fa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_ffd21ae7-1cf1-44f3-abbd-0133af4bed63" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_aa386a80-5bef-41cd-8c69-051c7f0602fa" xlink:to="loc_us-gaap_EquityComponentDomain_ffd21ae7-1cf1-44f3-abbd-0133af4bed63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_85158e1e-76be-4aa3-a6ed-15e68bea6198" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ffd21ae7-1cf1-44f3-abbd-0133af4bed63" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_85158e1e-76be-4aa3-a6ed-15e68bea6198" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_95cd99d1-c337-4058-9d7f-926d3d7ff2bc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_bbf310b2-dd44-4a8e-9cbf-200fc8898390" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_95cd99d1-c337-4058-9d7f-926d3d7ff2bc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_95cd99d1-c337-4058-9d7f-926d3d7ff2bc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_95cd99d1-c337-4058-9d7f-926d3d7ff2bc" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_95cd99d1-c337-4058-9d7f-926d3d7ff2bc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_d04ba707-67e1-47a1-ad25-c8598608d27e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_95cd99d1-c337-4058-9d7f-926d3d7ff2bc" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_d04ba707-67e1-47a1-ad25-c8598608d27e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_cd2c2701-04ae-4b8f-a511-c1ccefa58604" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_d04ba707-67e1-47a1-ad25-c8598608d27e" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_cd2c2701-04ae-4b8f-a511-c1ccefa58604" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/EARNINGSPERSHAREDetails" xlink:type="simple" xlink:href="cwst-20220930.xsd#EARNINGSPERSHAREDetails"/>
  <link:definitionLink xlink:role="http://casella.com/role/EARNINGSPERSHAREDetails" xlink:type="extended" id="i3175c50c13d8465d9a61bc41a063246f_EARNINGSPERSHAREDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_32474cb4-9efa-4789-9eab-12d5e35f476d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_e9691a60-e8b6-4852-9b86-2e6a2838e22f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_32474cb4-9efa-4789-9eab-12d5e35f476d" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_e9691a60-e8b6-4852-9b86-2e6a2838e22f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperations_26d35be9-1178-47fd-acbb-6a3ca128d6c5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeLossFromContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_e9691a60-e8b6-4852-9b86-2e6a2838e22f" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperations_26d35be9-1178-47fd-acbb-6a3ca128d6c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_1aef684a-12c3-420a-9e8d-adb932039d80" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_32474cb4-9efa-4789-9eab-12d5e35f476d" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_1aef684a-12c3-420a-9e8d-adb932039d80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_02eb993e-bb98-4e0d-9c39-3c0d46f7321d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_1aef684a-12c3-420a-9e8d-adb932039d80" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_02eb993e-bb98-4e0d-9c39-3c0d46f7321d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesRestrictedStock_fd1cc918-0d42-4407-bafa-70e7280bb3a5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfSharesRestrictedStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_1aef684a-12c3-420a-9e8d-adb932039d80" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesRestrictedStock_fd1cc918-0d42-4407-bafa-70e7280bb3a5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesIssuedBasic_e4ddb8d7-b50e-4d7b-9d0c-4e30934320dd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfSharesIssuedBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_1aef684a-12c3-420a-9e8d-adb932039d80" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesIssuedBasic_e4ddb8d7-b50e-4d7b-9d0c-4e30934320dd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_9f2f6b59-f50b-42c3-8a2a-d1b33b6af140" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_32474cb4-9efa-4789-9eab-12d5e35f476d" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_9f2f6b59-f50b-42c3-8a2a-d1b33b6af140" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_071d2da4-0438-47c6-8370-887a31c6fb93" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_32474cb4-9efa-4789-9eab-12d5e35f476d" xlink:to="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_071d2da4-0438-47c6-8370-887a31c6fb93" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_ab25c703-c350-4938-826c-934f437e1980" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_071d2da4-0438-47c6-8370-887a31c6fb93" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_ab25c703-c350-4938-826c-934f437e1980" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_5ecfd5f1-bf96-42e7-a1da-a90576bf7cb7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_32474cb4-9efa-4789-9eab-12d5e35f476d" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_5ecfd5f1-bf96-42e7-a1da-a90576bf7cb7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_ba267eb8-551a-4528-acd2-185f63d791b9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_32474cb4-9efa-4789-9eab-12d5e35f476d" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_ba267eb8-551a-4528-acd2-185f63d791b9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_a90c6d8c-0d59-479d-924f-6e43c84e8fb6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_32474cb4-9efa-4789-9eab-12d5e35f476d" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_a90c6d8c-0d59-479d-924f-6e43c84e8fb6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_888c4165-a789-403d-8b4c-9b8212d02ee6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_a90c6d8c-0d59-479d-924f-6e43c84e8fb6" xlink:to="loc_us-gaap_StatementClassOfStockAxis_888c4165-a789-403d-8b4c-9b8212d02ee6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_888c4165-a789-403d-8b4c-9b8212d02ee6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_888c4165-a789-403d-8b4c-9b8212d02ee6" xlink:to="loc_us-gaap_ClassOfStockDomain_888c4165-a789-403d-8b4c-9b8212d02ee6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_13a81489-86d1-41a6-baf0-7b70f62fdf10" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_888c4165-a789-403d-8b4c-9b8212d02ee6" xlink:to="loc_us-gaap_ClassOfStockDomain_13a81489-86d1-41a6-baf0-7b70f62fdf10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_568b875e-279d-4c55-b49a-75dd68264835" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_13a81489-86d1-41a6-baf0-7b70f62fdf10" xlink:to="loc_us-gaap_CommonClassAMember_568b875e-279d-4c55-b49a-75dd68264835" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_cbe95d57-42e8-4117-bdc4-1d3e3a927406" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_13a81489-86d1-41a6-baf0-7b70f62fdf10" xlink:to="loc_us-gaap_CommonClassBMember_cbe95d57-42e8-4117-bdc4-1d3e3a927406" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSRecurringFairValueMeasurementsDetail" xlink:type="simple" xlink:href="cwst-20220930.xsd#FAIRVALUEOFFINANCIALINSTRUMENTSRecurringFairValueMeasurementsDetail"/>
  <link:definitionLink xlink:role="http://casella.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSRecurringFairValueMeasurementsDetail" xlink:type="extended" id="ib91ba9296499439384196db6e6682e2b_FAIRVALUEOFFINANCIALINSTRUMENTSRecurringFairValueMeasurementsDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_18069cdb-6881-46c1-a3d6-5d67e857cf17" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_46a9144f-8513-424e-8be9-f758b0408a05" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_18069cdb-6881-46c1-a3d6-5d67e857cf17" xlink:to="loc_us-gaap_AssetsAbstract_46a9144f-8513-424e-8be9-f758b0408a05" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndInvestmentsNoncurrent_2f4c7a10-cb70-44c0-a71c-910ba090f8dc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCashAndInvestmentsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_46a9144f-8513-424e-8be9-f758b0408a05" xlink:to="loc_us-gaap_RestrictedCashAndInvestmentsNoncurrent_2f4c7a10-cb70-44c0-a71c-910ba090f8dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_77f2364f-b651-4f1a-af73-5abfb9d09081" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_46a9144f-8513-424e-8be9-f758b0408a05" xlink:to="loc_us-gaap_DerivativeAssets_77f2364f-b651-4f1a-af73-5abfb9d09081" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_67f774ee-3431-4783-acdd-ec4c6c26a234" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_46a9144f-8513-424e-8be9-f758b0408a05" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_67f774ee-3431-4783-acdd-ec4c6c26a234" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAbstract_a0413b2a-30ab-4d06-8913-87007f1379dd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_18069cdb-6881-46c1-a3d6-5d67e857cf17" xlink:to="loc_us-gaap_LiabilitiesAbstract_a0413b2a-30ab-4d06-8913-87007f1379dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateDerivativeLiabilitiesAtFairValue_955e6b19-5023-4e54-a5e8-b850c134c6ca" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestRateDerivativeLiabilitiesAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_a0413b2a-30ab-4d06-8913-87007f1379dd" xlink:to="loc_us-gaap_InterestRateDerivativeLiabilitiesAtFairValue_955e6b19-5023-4e54-a5e8-b850c134c6ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_839aae29-da36-437d-a4f9-491f6511d1c3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_18069cdb-6881-46c1-a3d6-5d67e857cf17" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_839aae29-da36-437d-a4f9-491f6511d1c3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_4d34c7ec-8129-43a2-90f8-6dbcc1474fd2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_839aae29-da36-437d-a4f9-491f6511d1c3" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_4d34c7ec-8129-43a2-90f8-6dbcc1474fd2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_4d34c7ec-8129-43a2-90f8-6dbcc1474fd2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_4d34c7ec-8129-43a2-90f8-6dbcc1474fd2" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_4d34c7ec-8129-43a2-90f8-6dbcc1474fd2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_6f30f5cf-cb49-4b49-94e4-5d0f9d480c05" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_4d34c7ec-8129-43a2-90f8-6dbcc1474fd2" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_6f30f5cf-cb49-4b49-94e4-5d0f9d480c05" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_a0cea5d1-6963-4737-b198-663654b2866d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_6f30f5cf-cb49-4b49-94e4-5d0f9d480c05" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_a0cea5d1-6963-4737-b198-663654b2866d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_83473963-e113-46f2-b223-d97884246d53" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_839aae29-da36-437d-a4f9-491f6511d1c3" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_83473963-e113-46f2-b223-d97884246d53" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_83473963-e113-46f2-b223-d97884246d53_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_83473963-e113-46f2-b223-d97884246d53" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_83473963-e113-46f2-b223-d97884246d53_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1f5c54c6-5e62-48d4-a217-caafb9331323" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_83473963-e113-46f2-b223-d97884246d53" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1f5c54c6-5e62-48d4-a217-caafb9331323" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_f978abe8-e932-4a61-9386-603a29279065" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1f5c54c6-5e62-48d4-a217-caafb9331323" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_f978abe8-e932-4a61-9386-603a29279065" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_14b74cd1-27b0-49a5-8c94-2cd289251fcc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1f5c54c6-5e62-48d4-a217-caafb9331323" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_14b74cd1-27b0-49a5-8c94-2cd289251fcc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_f1659cb0-812e-4c13-939e-372a73f5faa2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1f5c54c6-5e62-48d4-a217-caafb9331323" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_f1659cb0-812e-4c13-939e-372a73f5faa2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e39e2d91-fc73-442b-9211-cfb67ec83fff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_839aae29-da36-437d-a4f9-491f6511d1c3" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e39e2d91-fc73-442b-9211-cfb67ec83fff" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e39e2d91-fc73-442b-9211-cfb67ec83fff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e39e2d91-fc73-442b-9211-cfb67ec83fff" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e39e2d91-fc73-442b-9211-cfb67ec83fff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_d698fea7-8ccd-4f91-ae64-2c42776f0a94" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e39e2d91-fc73-442b-9211-cfb67ec83fff" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_d698fea7-8ccd-4f91-ae64-2c42776f0a94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandfillMember_7e2b6cf1-146a-468a-bb11-5a96acd3a6fc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LandfillMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_d698fea7-8ccd-4f91-ae64-2c42776f0a94" xlink:to="loc_us-gaap_LandfillMember_7e2b6cf1-146a-468a-bb11-5a96acd3a6fc" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSAdditionalInformationDetail" xlink:type="simple" xlink:href="cwst-20220930.xsd#FAIRVALUEOFFINANCIALINSTRUMENTSAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://casella.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSAdditionalInformationDetail" xlink:type="extended" id="ie3c3c96df68840b0ab227606dc769957_FAIRVALUEOFFINANCIALINSTRUMENTSAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_9bd8236f-e9e8-4360-aed7-1d96d5a2ac10" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFairValue_40bea13d-922f-45b9-a4c8-317d989071bc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9bd8236f-e9e8-4360-aed7-1d96d5a2ac10" xlink:to="loc_us-gaap_DebtInstrumentFairValue_40bea13d-922f-45b9-a4c8-317d989071bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_4cdfbcf9-ab16-4fe3-9daa-b0baf3697f46" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9bd8236f-e9e8-4360-aed7-1d96d5a2ac10" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_4cdfbcf9-ab16-4fe3-9daa-b0baf3697f46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LinesOfCreditFairValueDisclosure_5b2958c5-0138-4e75-9b8b-82c4c00ac00e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LinesOfCreditFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9bd8236f-e9e8-4360-aed7-1d96d5a2ac10" xlink:to="loc_us-gaap_LinesOfCreditFairValueDisclosure_5b2958c5-0138-4e75-9b8b-82c4c00ac00e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_0e005fdb-4e1e-47f2-9a84-60bbf8645e4e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9bd8236f-e9e8-4360-aed7-1d96d5a2ac10" xlink:to="loc_us-gaap_DebtInstrumentTable_0e005fdb-4e1e-47f2-9a84-60bbf8645e4e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_892b3831-c404-47ef-8280-46e49f483366" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0e005fdb-4e1e-47f2-9a84-60bbf8645e4e" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_892b3831-c404-47ef-8280-46e49f483366" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_892b3831-c404-47ef-8280-46e49f483366_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_892b3831-c404-47ef-8280-46e49f483366" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_892b3831-c404-47ef-8280-46e49f483366_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_c0891c44-e31c-4bd6-b177-d29a06a6a6ca" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_892b3831-c404-47ef-8280-46e49f483366" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_c0891c44-e31c-4bd6-b177-d29a06a6a6ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_d7a8ee8c-a119-409b-8ea3-493c0f93bc8a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_c0891c44-e31c-4bd6-b177-d29a06a6a6ca" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_d7a8ee8c-a119-409b-8ea3-493c0f93bc8a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_47c2b544-1941-472d-bdb1-796687324106" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_d7a8ee8c-a119-409b-8ea3-493c0f93bc8a" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_47c2b544-1941-472d-bdb1-796687324106" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_b76a0437-1176-4dab-b262-40c479bbc72d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_d7a8ee8c-a119-409b-8ea3-493c0f93bc8a" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_b76a0437-1176-4dab-b262-40c479bbc72d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_0286dfa0-f39e-4c44-81e4-4b8b2cd52bbf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0e005fdb-4e1e-47f2-9a84-60bbf8645e4e" xlink:to="loc_us-gaap_DebtInstrumentAxis_0286dfa0-f39e-4c44-81e4-4b8b2cd52bbf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_0286dfa0-f39e-4c44-81e4-4b8b2cd52bbf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_0286dfa0-f39e-4c44-81e4-4b8b2cd52bbf" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_0286dfa0-f39e-4c44-81e4-4b8b2cd52bbf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_ecdee939-76f7-4d49-8fc0-4d77154fafbd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_0286dfa0-f39e-4c44-81e4-4b8b2cd52bbf" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_ecdee939-76f7-4d49-8fc0-4d77154fafbd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_AmendedTermAFacilityDueDecember2026TermLoanBFacilityMember_3da8216f-b6f0-4b67-957a-099f1fbcab96" xlink:href="cwst-20220930.xsd#cwst_AmendedTermAFacilityDueDecember2026TermLoanBFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_ecdee939-76f7-4d49-8fc0-4d77154fafbd" xlink:to="loc_cwst_AmendedTermAFacilityDueDecember2026TermLoanBFacilityMember_3da8216f-b6f0-4b67-957a-099f1fbcab96" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_30a18d7c-53c5-47d0-a791-965544c35551" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0e005fdb-4e1e-47f2-9a84-60bbf8645e4e" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_30a18d7c-53c5-47d0-a791-965544c35551" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_30a18d7c-53c5-47d0-a791-965544c35551_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_30a18d7c-53c5-47d0-a791-965544c35551" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_30a18d7c-53c5-47d0-a791-965544c35551_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_17c47d15-70b8-4d2e-88b5-154daf39ea6a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_30a18d7c-53c5-47d0-a791-965544c35551" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_17c47d15-70b8-4d2e-88b5-154daf39ea6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_FixedRateBondsMember_aeb6a130-9d40-42a8-8771-d2426883ed73" xlink:href="cwst-20220930.xsd#cwst_FixedRateBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_17c47d15-70b8-4d2e-88b5-154daf39ea6a" xlink:to="loc_cwst_FixedRateBondsMember_aeb6a130-9d40-42a8-8771-d2426883ed73" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_e3f68257-851d-4ef3-a165-a0d2afb91dd5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_17c47d15-70b8-4d2e-88b5-154daf39ea6a" xlink:to="loc_us-gaap_SecuredDebtMember_e3f68257-851d-4ef3-a165-a0d2afb91dd5" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/SEGMENTREPORTINGSummaryofFinancialInformationbyReportableSegmentDetail" xlink:type="simple" xlink:href="cwst-20220930.xsd#SEGMENTREPORTINGSummaryofFinancialInformationbyReportableSegmentDetail"/>
  <link:definitionLink xlink:role="http://casella.com/role/SEGMENTREPORTINGSummaryofFinancialInformationbyReportableSegmentDetail" xlink:type="extended" id="iea4f49158c4843a9a5ba240543c6ef06_SEGMENTREPORTINGSummaryofFinancialInformationbyReportableSegmentDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_0b1beaa6-3770-4ed3-876f-2faf3e697ccb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_cb5ba2bc-e95e-41ac-9d75-d678dfcc9080" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_0b1beaa6-3770-4ed3-876f-2faf3e697ccb" xlink:to="loc_us-gaap_Revenues_cb5ba2bc-e95e-41ac-9d75-d678dfcc9080" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_24cad3c5-fb18-4528-846f-9d75cac8030a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_0b1beaa6-3770-4ed3-876f-2faf3e697ccb" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_24cad3c5-fb18-4528-846f-9d75cac8030a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_cd0f70bb-cc67-4d1c-827e-1a23b41e4a26" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_0b1beaa6-3770-4ed3-876f-2faf3e697ccb" xlink:to="loc_us-gaap_OperatingIncomeLoss_cd0f70bb-cc67-4d1c-827e-1a23b41e4a26" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_28ec344b-0c8b-4447-a391-172451be2383" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_0b1beaa6-3770-4ed3-876f-2faf3e697ccb" xlink:to="loc_us-gaap_Assets_28ec344b-0c8b-4447-a391-172451be2383" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_83c84164-c25c-4ae4-8830-1786affa4549" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_0b1beaa6-3770-4ed3-876f-2faf3e697ccb" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_83c84164-c25c-4ae4-8830-1786affa4549" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_12cd48b7-8176-4ec8-b73d-0699be3de985" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_83c84164-c25c-4ae4-8830-1786affa4549" xlink:to="loc_srt_ConsolidationItemsAxis_12cd48b7-8176-4ec8-b73d-0699be3de985" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_12cd48b7-8176-4ec8-b73d-0699be3de985_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_12cd48b7-8176-4ec8-b73d-0699be3de985" xlink:to="loc_srt_ConsolidationItemsDomain_12cd48b7-8176-4ec8-b73d-0699be3de985_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_cd776ee5-e33d-453e-80e2-c8dc28fe97d5" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_12cd48b7-8176-4ec8-b73d-0699be3de985" xlink:to="loc_srt_ConsolidationItemsDomain_cd776ee5-e33d-453e-80e2-c8dc28fe97d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_bc914bd6-12d0-4a50-95d4-8140023ee78c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_cd776ee5-e33d-453e-80e2-c8dc28fe97d5" xlink:to="loc_us-gaap_OperatingSegmentsMember_bc914bd6-12d0-4a50-95d4-8140023ee78c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_f9879e70-39ed-4a96-afbe-002d07260fcb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_cd776ee5-e33d-453e-80e2-c8dc28fe97d5" xlink:to="loc_us-gaap_CorporateNonSegmentMember_f9879e70-39ed-4a96-afbe-002d07260fcb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_8bde7205-73bb-491b-8dcc-ad8dfbd3c98c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_cd776ee5-e33d-453e-80e2-c8dc28fe97d5" xlink:to="loc_us-gaap_IntersegmentEliminationMember_8bde7205-73bb-491b-8dcc-ad8dfbd3c98c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_125f0add-ea51-4266-90ff-43f55a257b51" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_83c84164-c25c-4ae4-8830-1786affa4549" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_125f0add-ea51-4266-90ff-43f55a257b51" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_125f0add-ea51-4266-90ff-43f55a257b51_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_125f0add-ea51-4266-90ff-43f55a257b51" xlink:to="loc_us-gaap_SegmentDomain_125f0add-ea51-4266-90ff-43f55a257b51_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_63a8b960-1923-46bf-8d7b-5363c72ef3b0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_125f0add-ea51-4266-90ff-43f55a257b51" xlink:to="loc_us-gaap_SegmentDomain_63a8b960-1923-46bf-8d7b-5363c72ef3b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_EasternRegionMember_e68e5627-b04d-463b-bfc7-4428998b70fb" xlink:href="cwst-20220930.xsd#cwst_EasternRegionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_63a8b960-1923-46bf-8d7b-5363c72ef3b0" xlink:to="loc_cwst_EasternRegionMember_e68e5627-b04d-463b-bfc7-4428998b70fb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_WesternRegionMember_231d286e-52eb-4704-a4c6-98c810622d78" xlink:href="cwst-20220930.xsd#cwst_WesternRegionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_63a8b960-1923-46bf-8d7b-5363c72ef3b0" xlink:to="loc_cwst_WesternRegionMember_231d286e-52eb-4704-a4c6-98c810622d78" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_ResourceSolutionsRegionMember_11696b85-51b7-48be-b6fc-0c5c4541b0ca" xlink:href="cwst-20220930.xsd#cwst_ResourceSolutionsRegionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_63a8b960-1923-46bf-8d7b-5363c72ef3b0" xlink:to="loc_cwst_ResourceSolutionsRegionMember_11696b85-51b7-48be-b6fc-0c5c4541b0ca" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://casella.com/role/SEGMENTREPORTINGSummaryofRevenuesAttributabletoServicesProvidedbyCompanyDetail" xlink:type="simple" xlink:href="cwst-20220930.xsd#SEGMENTREPORTINGSummaryofRevenuesAttributabletoServicesProvidedbyCompanyDetail"/>
  <link:definitionLink xlink:role="http://casella.com/role/SEGMENTREPORTINGSummaryofRevenuesAttributabletoServicesProvidedbyCompanyDetail" xlink:type="extended" id="i7bac23a25d5c418293f2992e93f3f2f5_SEGMENTREPORTINGSummaryofRevenuesAttributabletoServicesProvidedbyCompanyDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_566c7639-347d-41ad-bb3d-4a0d764567c2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_5ce75d5f-727f-4911-b28f-31b54d73cbd8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_566c7639-347d-41ad-bb3d-4a0d764567c2" xlink:to="loc_us-gaap_Revenues_5ce75d5f-727f-4911-b28f-31b54d73cbd8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_9780f2ad-b557-4d01-82e1-08f3feee442d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_566c7639-347d-41ad-bb3d-4a0d764567c2" xlink:to="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_9780f2ad-b557-4d01-82e1-08f3feee442d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_b7c3ba7a-4db9-452c-a6d8-356ce820b1f9" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_9780f2ad-b557-4d01-82e1-08f3feee442d" xlink:to="loc_srt_ProductOrServiceAxis_b7c3ba7a-4db9-452c-a6d8-356ce820b1f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_b7c3ba7a-4db9-452c-a6d8-356ce820b1f9_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_b7c3ba7a-4db9-452c-a6d8-356ce820b1f9" xlink:to="loc_srt_ProductsAndServicesDomain_b7c3ba7a-4db9-452c-a6d8-356ce820b1f9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_d9da5b49-5436-4d01-8856-177d350f02f5" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_b7c3ba7a-4db9-452c-a6d8-356ce820b1f9" xlink:to="loc_srt_ProductsAndServicesDomain_d9da5b49-5436-4d01-8856-177d350f02f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_SolidWasteOperationsMember_07c546bc-643e-4dd8-9c9e-394edb0d71f3" xlink:href="cwst-20220930.xsd#cwst_SolidWasteOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d9da5b49-5436-4d01-8856-177d350f02f5" xlink:to="loc_cwst_SolidWasteOperationsMember_07c546bc-643e-4dd8-9c9e-394edb0d71f3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_SolidWasteOperationsCollectionMember_8ba6322a-2493-458d-ae32-951687d1ee5b" xlink:href="cwst-20220930.xsd#cwst_SolidWasteOperationsCollectionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cwst_SolidWasteOperationsMember_07c546bc-643e-4dd8-9c9e-394edb0d71f3" xlink:to="loc_cwst_SolidWasteOperationsCollectionMember_8ba6322a-2493-458d-ae32-951687d1ee5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_SolidWasteOperationsDisposalMember_9aa37922-7727-44f2-96e3-f00f37d268ef" xlink:href="cwst-20220930.xsd#cwst_SolidWasteOperationsDisposalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cwst_SolidWasteOperationsMember_07c546bc-643e-4dd8-9c9e-394edb0d71f3" xlink:to="loc_cwst_SolidWasteOperationsDisposalMember_9aa37922-7727-44f2-96e3-f00f37d268ef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_SolidWasteOperationsPowerGenerationMember_8308a320-76fa-4abb-94a9-c83036a453c3" xlink:href="cwst-20220930.xsd#cwst_SolidWasteOperationsPowerGenerationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cwst_SolidWasteOperationsMember_07c546bc-643e-4dd8-9c9e-394edb0d71f3" xlink:to="loc_cwst_SolidWasteOperationsPowerGenerationMember_8308a320-76fa-4abb-94a9-c83036a453c3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_SolidWasteOperationsProcessingMember_6b22ecf6-bd52-4686-a4c8-3ef00eb00a1c" xlink:href="cwst-20220930.xsd#cwst_SolidWasteOperationsProcessingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cwst_SolidWasteOperationsMember_07c546bc-643e-4dd8-9c9e-394edb0d71f3" xlink:to="loc_cwst_SolidWasteOperationsProcessingMember_6b22ecf6-bd52-4686-a4c8-3ef00eb00a1c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_ResourceSolutionsOperationsMember_e8732ccc-d234-4382-b7aa-13a83c0adb1a" xlink:href="cwst-20220930.xsd#cwst_ResourceSolutionsOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d9da5b49-5436-4d01-8856-177d350f02f5" xlink:to="loc_cwst_ResourceSolutionsOperationsMember_e8732ccc-d234-4382-b7aa-13a83c0adb1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_ResourceSolutionsOperationsProcessingMember_fa0ef128-06dc-4f1c-8e40-e3ec5776ba0f" xlink:href="cwst-20220930.xsd#cwst_ResourceSolutionsOperationsProcessingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cwst_ResourceSolutionsOperationsMember_e8732ccc-d234-4382-b7aa-13a83c0adb1a" xlink:to="loc_cwst_ResourceSolutionsOperationsProcessingMember_fa0ef128-06dc-4f1c-8e40-e3ec5776ba0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cwst_ResourceSolutionsOperationsNonProcessingMember_29d7301b-ace0-4429-acd4-346c4aa062ea" xlink:href="cwst-20220930.xsd#cwst_ResourceSolutionsOperationsNonProcessingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cwst_ResourceSolutionsOperationsMember_e8732ccc-d234-4382-b7aa-13a83c0adb1a" xlink:to="loc_cwst_ResourceSolutionsOperationsNonProcessingMember_29d7301b-ace0-4429-acd4-346c4aa062ea" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-roles-2022.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
