| C | Degrees Celsius (centigrade) |
| c | centi (0.01 = 10-2) |
| C & R | Communications and radar |
| c sups | Combat supplies |
| C-Band | 3 700 to 4 200 MHz |
| C/N | Carrier-to-noise ratio (radio) |
| c/s | Call sign |
| C2/C2 | Command and control |
| C3/C3 | Command, control and communications |
| C3CM/C3CM | Command, control and communications countermeasures |
| C3I/C3I | Command, control, communications and intelligence |
| C4I/C4I | Command, control, communications, computers and intelligence |
| CA | Controller, aircraft |
| Counter-air |
| ca | circa (approximately) |
| CAA | Civil Aviation Authority |
| Co-ordinating Approval Authority |
| Collision avoidance aid |
| CAAIS | Computer-assisted action information system |
| CABA | Compressed air breathing apparatus |
| CAC | Combined approach control |
| CACC | Civil aviation control centre |
| CACS | Computer-assisted command system |
| CAD | Central ammunition depot |
| Computer-aided design |
| CAD/CAM | Computer-aided design and manufacture |
| CADMID | Concept, assessment, demonstration, manufacture, in-service and disposal (cycle) |
| CADS | Controlled aerial delivery system |
| CADWS | Close air defence weapon system |
| CAE | Common applications environment (computers) |
| CAI | Computer-aided instruction |
| cal | Calibre |
| CALM | Catenary anchor leg mooring |
| Crane attachment, lorry-mounted |
| CALS | Computer-aided logistic support |
| Continuous acquisition and life-cycle support |
| CAM | Computer-aided manufacturing |
| cam | Camouflage |
| CAMBS | Command active multi-beam sonobuoy |
| CAMPS | Computer-aided message processing system |
| CANE | Computer-aided navigation equipment |
| Computer-assisted navigation equipment |
| CAO | Cargo aircraft only |
| CAP | Combat air patrol |
| Company aid post |
| Computer-aided planning |
| CAPS | Conventional armaments planning system |
| CAPSIN | Civil aviation packet-switched integrated network |
| Capt | Captain |
| CARM | Chemical agent resistant material |
| CARMS | Civil aviation radio measuring station |
| CAS | Calibrated air speed |
| Chief of Air Staff |
| Close air support |
| Collision avoidance system |
| Command augmentation system |
| Computed air speed |
| Controlled air space |
| cas | Casualty |
| CASCAD | Close air support cargo dispenser |
| CASE | Computer-aided software engineering |
| casevac | Casualty evacuation |
| CASOM | Conventionally armed stand-off missile |
| CASOR | Civil air space operations room |
| CASTOR | Corps airborne stand-off radar |
| CAT | Civil air traffic |
| Clear air turbulence |
| Computerised axial tomography |
| cat | Category |
| Catering |
| CATC | College of Air Traffic Control |
| Commonwealth Air Transport Council |
| CATO | Civil air traffic operations |
| CAV | Constant angular velocity |
| CAVOK | Ceiling and visibility OK |
| CAVU | Ceiling and visibility unrestricted |
| CB | Centre of buoyancy |
| CBDE | Chemical and Biological Defence Establishment |
| CBI | Computer-based instruction |
| Confederation of British Industry |
| CBM | Confidence-building measures |
| Conventional buoy marking |
| CBR | Chemical, biological and radiological |
| CBRN | Chemical, biological, radiological and nuclear |
| CBRNE | Chemical, biological, radiological, nuclear and explosive |
| CBT | Clean ballast tank |
| Computer-based training |
| CBU | Cluster bomb unit |
| CC | Command and control (C²) |
| CCB | Configuration control board |
| CCC | Command, control and communications (C³) |
| CCCCM | Command, control and communications counter-measures (C³CM) |
| CCCI | Command, control, communications and information (C³I) |
| Command, control, communications and intelligence (C³I) |
| CCCS | Command, control and communications system (C³S) |
| CCD | Camouflage, concealment and deception |
| Charge-coupled device |
| CCDS | Code callsign distribution system |
| CCF | Common control function |
| CCGT | Combined cycle gas turbine |
| CCIP | Continuously computed impact point |
| CCIR | Comité Consultatif International des Radiocommunications (International Radio Consultative Committee) |
| CCIS | Command, control and information system |
| CCITT | Comité Consultatif International Télégraphique et Téléphonique (International Telegraph and Telephone Consultative Committee) |
| CCLRC | Council for the Central Laboratory of the Research Councils |
| CCM | Counter-counter-measure |
| CCP | Casualty collecting post |
| CCRP | Continuously computed release point |
| CCS | Casualty clearing station |
| Command and control system |
| CCTA | Central Computer and Telecommunications Agency |
| CCTV | Closed-circuit television |
| CCU | Crypto control unit |
| CD | Civil defence |
| CDAA | Circularly differential antenna array |
| CDB | Central data bank (Eurocontrol) |
| CDC | Civil defence committee |
| CDE | Chemical Defence Establishment |
| CDL | Chief of Defence Logistics |
| CDM | Clean development mechanism |
| CDMA | Code division multiple access |
| CDP | Chief of Defence Procurement |
| CDRL | Contract data requirement list |
| CDS | Collimated display system |
| CDU | Chart display unit |
| Control and display unit |
| CE | Centre of effort (sail) |
| Circular error |
| Communications electronics |
| Concept exploration |
| Concurrent engineering |
| CEAC | Committee for European Airspace Coordination |
| CELT | Crypto equipment for low-speed telegraphy |
| CEO | Chief Executive Officer |
| CEOS | Committee on Earth Observation Satellites (of UN) |
| CEP | Capital expenditure programme |
| Central Europe Pipeline |
| Central engineer park |
| Circular error of probability |
| Civil emergency planning |
| Computed error probability |
| CEPAS | Crypto equipment for packet switching |
| CER | Communications equipment room |
| CERD | Computer entry and read-out device |
| CERN | Conseil Européen pour la Recherche Nucléaire |
| CEROFF | Cypher equipment rapid off-line |
| CES | Coast earth station (satellite) |
| CET | Combat engineer tractor |
| Computer-enhanced training |
| CEV | Combat engineer vehicle |
| CEW | Counter-electronic warfare |
| CF | Centre of flotation |
| CFAR | Constant false alarm rate |
| CFC | Chlorofluorocarbon |
| CFD | Computational fluid dynamics |
| CFI | Cost, freight and insurance |
| CFIT | Controlled flight into terrain |
| CFMU | Central flow management unit (Eurocontrol) |
| CFRP | Carbon fibre reinforced plastics |
| CFS | Container freight station |
| CFSO | Chief fire service officer |
| CG | Centre of gravity |
| Computer graphics |
| CGI | Computer-generated image |
| Cruise guide indicator (helicopter) |
| cgs | Centimetre-gram-second (system of measurement) |
| CH | Custom house |
| CHIRP | Confidential human factors incident reporting system |
| CHOP | Change of operational procedures |
| CHOTS | Corporate headquarters office technology system |
| CHP | Combined heat and power |
| CI | Compression ignition |
| Counter-insurgency |
| Counter-intelligence |
| CIAS | Civil industrial access scheme |
| CIBS | Chartered Institute of Building Services |
| CIC | Combat information centre |
| CIDIN | Common ICAO data interchange network |
| CIF | Custom, insurance and freight |
| CIFS | Common internet file system |
| CIG | Computer image generator |
| Current intelligence group |
| CIJ | Close-in jamming |
| CIM | Computer-integrated manufacturing |
| CIMIC | Civilian-military co-operation |
| CinC | Commander in Chief |
| CIP | Communications improvement plan |
| CIPC | Coastal patrol interdiction craft |
| CIRPLS | Computer integration of requirements, procurement and logistic support |
| CIS | Communication and Information Systems |
| CISC | Complex instruction set computer |
| CIT | Chartered Institute of Transport |
| CITIS | Contractors´ integrated technical information services |
| civ | Civil |
| Civilian |
| CIWS | Close-in weapon system |
| CKD | Completely knocked down |
| CL | Centre line |
| CLA | Cargo loading adaptability |
| CLOTS | Container loading, off-loading and transfer system |
| CLR | Centre of lateral resistance (sail) |
| CLRC | Central Laboratory of the Research Councils |
| CLS | Contractorised logistic support |
| CLV | Constant linear velocity |
| CM | Capability manager |
| Change management |
| Configuration management |
| Cruise missile |
| CMC | Central maintenance computer |
| CME | Coronal mass ejection |
| CMF | Conceptual military framework |
| CMG | Course made good (nav) |
| CMM | Cargo movement module |
| CMO | Chief Medical Officer |
| CMOP | Configuration management operating plan |
| CMOS | Complementary metal oxide semiconductor |
| CMS | Central maintenance section |
| Central maintenance system |
| CMU | Central maintenance unit |
| CNAD | Conference of National Armaments Directors |
| CNC | Computer numerically controlled (machine tool) |
| CNGF | Common new generation frigate |
| CNI | Communications, navigation, identification |
| CNIS | Channel Navigation Information Service |
| CNR | Combat net radio |
| CNS | Communications, navigation, surveillance (function) |
| CO | Commanding officer |
| COB | Co-located operating base |
| COBOL | Common business-oriented language (computer) |
| COC | Combat operations centre |
| COD | Carrier-on-board delivery |
| Cash on delivery |
| Chemical oxygen demand |
| CODASYL | Conference on Data System Language |
| COFDM | Coded orthogonal frequency-division multiplexing |
| COFFA | Certificate of final financial acceptance |
| colat | Complement of latitude (nav) |
| COLOC | Change of location of command |
| COLPRO | Collective protection |
| colregs | Collision regulations |
| COM | Computer output microfilm |
| com | Communication |
| comcen | Communications centre |
| comd | Command/commander |
| comint | Communications intelligence |
| comlink | Communications link |
| comms | Communications |
| comprat | Composite rations (compo) |
| comsat | Communications satellite |
| comsec | Communications security |
| coord | Coordinate |
| COP | Close observation plan |
| Contingency operation plan |
| COPS | Common operational performance specification |
| cor | Correction |
| COS | Chief of Staff |
| COSHH | Control of substances hazardous to health |
| COTS | Commercial off-the-shelf (equipment) |
| COW | Crude oil washing (tankers) |
| coy | Company |
| CP | Centre of pressure |
| Change proposal |
| Close protection |
| Code of practice |
| Command post |
| Contact point |
| Critical point |
| CP/M | Control program for microcomputers |
| CPA | Closest point of approach (nav) |
| CPC | Certificate of professional competence |
| Chemical protective clothing |
| CPCI | Compact peripheral component interconnect |
| CPIF | Cost plus incentive fee |
| CPL | Commercial pilot´s licence |
| Common programming language |
| CPM | Control program for microcomputers |
| Critical path method |
| CPO | Chief petty officer |
| CPP | Controllable pitch propeller |
| CPT | Cockpit procedures trainer |
| CPU | Central processing unit (computer) |
| CPV | Concrete pressure vessel |
| CQB | Close-quarter battle |
| CQBR | Close-quarter battle range |
| CQMS | Company quartermaster sergeant |
| CR | Central region |
| Confidential report |
| CRB | Change review board |
| CRC | Control and reporting centre |
| CRDF | Cathode ray direction finder |
| CRIP | Crisis resupply-from-industry procedure |
| CRM | Crew resource management |
| Customer relations management |
| CRP | Carbon fibre-reinforced plastics |
| Compressed raster product (geo) |
| Control and reporting post |
| Counter-rotating propellers |
| CRS | Coastal radio station |
| Control and reporting system |
| CRT | Cathode ray tube |
| Communications receiver/transmitter |
| CS | Carson and Staughton (tear gas) |
| Continental shelf |
| CSA | Customer-supplier agreement |
| CSAR | Combat search and rescue |
| CSBM | Confidence and security-building measure |
| CSD | Closed shelter deck |
| CSDU | Core service data unit |
| CSI | Commercial satellite imagery |
| CSO | Continental shelf operator |
| CSP | Contractor´s spares package |
| CSS | Combat service support |
| CSV | Comma-separated variable |
| CT1 | Cordless telephone (analogue standard) |
| CT2 | Cordless telephone (digital standard) |
| CTA | Control area |
| CTD | Conductivity, temperature and depth (oceanology) |
| CTM | Capacity in ton-miles |
| CTOL | Conventional take-off and landing (aircraft) |
| CTR | Close target reconnaissance |
| Controlled terminal region |
| CTS | Central tactical system (Royal Navy) |
| Computerised test system |
| CTZ | Control zone |
| CUTE | Common user terminal equipment |
| CV | Combat vehicle |
| CVD | Central vehicle depot |
| CVFR | Controlled visual flight rules |
| CVR | Cockpit voice recorder |
| Crystal video receiver |
| CVR(T) | Combat vehicle, reconnaissance (tracked) |
| CVR(W) | Combat vehicle, reconnaissance (wheeled) |
| CVT | Continuously variable traction |
| CW | Chemical warfare |
| Continuous wave (radio) |
| CWG | Capability working group |
| CWL | Calm water line |
| cwy | Clearway |
| CZ | Contiguous zone |
| CZCS | Combat zone communications system |
| CZD | Calculated zenith distance (nav) |
| CZM | Coastal zone management |
