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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019ff59e-b95e-775c-aea3-52da0c8f388a,g:c9ec6f39-687d-4ee8-b445-9ef4466b9c17-->
<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://www.cycurion.com/role/Cover" xlink:type="simple" xlink:href="cycu-20260807.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.cycurion.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_019ff59e-b95e-7ba5-b805-e4d79b470b4b" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_DocumentInformationTable_019ff59e-b95e-7ba5-b805-e4d79b470b4b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019ff59e-b95e-7472-97e7-678488880c6a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_019ff59e-b95e-7ba5-b805-e4d79b470b4b" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019ff59e-b95e-7472-97e7-678488880c6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019ff59e-b95e-7472-97e7-678488880c6a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019ff59e-b95e-7472-97e7-678488880c6a" xlink:to="loc_us-gaap_EquityComponentDomain_019ff59e-b95e-7472-97e7-678488880c6a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019ff59e-b95e-75bd-bbf7-4cd613f509dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019ff59e-b95e-7472-97e7-678488880c6a" xlink:to="loc_us-gaap_EquityComponentDomain_019ff59e-b95e-75bd-bbf7-4cd613f509dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019ff59e-b95e-7ff6-9a52-0756e76eeb28" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ff59e-b95e-75bd-bbf7-4cd613f509dd" xlink:to="loc_us-gaap_CommonStockMember_019ff59e-b95e-7ff6-9a52-0756e76eeb28" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_019ff59e-b95e-77f3-a916-63b72ec85e5c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ff59e-b95e-75bd-bbf7-4cd613f509dd" xlink:to="loc_us-gaap_WarrantMember_019ff59e-b95e-77f3-a916-63b72ec85e5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019ff59e-b95e-7238-980e-e341dcdf5e09" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_DocumentType_019ff59e-b95e-7238-980e-e341dcdf5e09" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019ff59e-b95e-7085-8541-a9590c00e7c3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_DocumentPeriodEndDate_019ff59e-b95e-7085-8541-a9590c00e7c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019ff59e-b95e-7225-b0a7-e0d51b00e8fa" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_EntityRegistrantName_019ff59e-b95e-7225-b0a7-e0d51b00e8fa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019ff59e-b95e-7bac-9b33-d009a7141aa2" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019ff59e-b95e-7bac-9b33-d009a7141aa2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019ff59e-b95e-77cc-9014-bbbe6b33cb04" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_EntityFileNumber_019ff59e-b95e-77cc-9014-bbbe6b33cb04" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019ff59e-b95e-719c-ac28-2ee872abd7ea" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_EntityTaxIdentificationNumber_019ff59e-b95e-719c-ac28-2ee872abd7ea" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019ff59e-b95e-7adf-8f1a-fe4439bd5cd3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_EntityAddressAddressLine1_019ff59e-b95e-7adf-8f1a-fe4439bd5cd3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_019ff59e-b95e-783f-bd9a-e3f0cf5b78d4" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_EntityAddressAddressLine2_019ff59e-b95e-783f-bd9a-e3f0cf5b78d4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019ff59e-b95e-7767-b0ec-8f431cb6c44e" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_EntityAddressCityOrTown_019ff59e-b95e-7767-b0ec-8f431cb6c44e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019ff59e-b95e-7970-93f8-6d59105b2559" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_EntityAddressStateOrProvince_019ff59e-b95e-7970-93f8-6d59105b2559" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019ff59e-b95e-767f-837d-b2a73626e28a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_EntityAddressPostalZipCode_019ff59e-b95e-767f-837d-b2a73626e28a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019ff59e-b95e-767a-9561-aa4145ebb20c" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_CityAreaCode_019ff59e-b95e-767a-9561-aa4145ebb20c" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019ff59e-b95e-75f4-a5d0-840d3963fe0e" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_LocalPhoneNumber_019ff59e-b95e-75f4-a5d0-840d3963fe0e" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_019ff59e-b95e-7a66-bef6-4e56b8fcebd8" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_WrittenCommunications"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_WrittenCommunications_019ff59e-b95e-7a66-bef6-4e56b8fcebd8" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_019ff59e-b95e-7f59-b603-84f51fe3f793" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SolicitingMaterial"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_SolicitingMaterial_019ff59e-b95e-7f59-b603-84f51fe3f793" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_019ff59e-b95e-7f62-9b6c-300910a638aa" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_PreCommencementTenderOffer_019ff59e-b95e-7f62-9b6c-300910a638aa" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_019ff59e-b95e-75ad-b142-f068238b6709" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_019ff59e-b95e-75ad-b142-f068238b6709" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019ff59e-b95e-7908-b6ab-d1a8d448baa6" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_Security12bTitle_019ff59e-b95e-7908-b6ab-d1a8d448baa6" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019ff59e-b95e-71b2-b572-5eeb5f97ed9b" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_TradingSymbol_019ff59e-b95e-71b2-b572-5eeb5f97ed9b" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019ff59e-b95e-7989-86f5-c8bfc576143a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_SecurityExchangeName_019ff59e-b95e-7989-86f5-c8bfc576143a" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019ff59e-b95e-7b9c-b2a9-46d3dc6b8848" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_EntityEmergingGrowthCompany_019ff59e-b95e-7b9c-b2a9-46d3dc6b8848" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityExTransitionPeriod_019ff59e-b95e-7c8d-a3f7-c05b2c1441e8" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityExTransitionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_EntityExTransitionPeriod_019ff59e-b95e-7c8d-a3f7-c05b2c1441e8" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019ff59e-b95e-72fb-b115-094985f1e28d" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_EntityCentralIndexKey_019ff59e-b95e-72fb-b115-094985f1e28d" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019ff59e-b95e-7da8-bb4c-9bff1dce7333" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ff59e-b95e-7da1-bc98-3c7fc74aac54" xlink:to="loc_dei_AmendmentFlag_019ff59e-b95e-7da8-bb4c-9bff1dce7333" xlink:type="arc" order="23"/>
  </link:definitionLink>
</link:linkbase>
