| Abbreviation | Definition |
|---|---|
| CIRAS | Combat Integrated Releasable Armor System |
| CIRCA | Clandestine Insurgent Rebel Clown Army |
| CIRCII | Central Information Reference and Control II |
| CIRCM | Common Infrared Countermeasures program |
| CIRCUIT-A | Counter-Insurgency Rescue Combat Unit Intercepting Terrorist Activity |
| CIRIS | Completely Integrated Reference Instrumentation |
| CIRM | Centro Internazionale Radio Medico (International Radio-Medical Center) |
| CIRN | Commanders Information Report Network |
| CIRT | Critical Incident Response Team |
| CIRV | Common Interswitch Rekeying Variable |
| CIRVIS | Communications Instructions for Reporting Vital Intelligence Sightings |
| CIS | Capital Investment Strategy |
| CIS | Combat Identification System |
| CIS | Command Information System |
| CIS | Common Item Support |
| CIS | Commonwealth of Independent States |
| CIS | Communications Interface Shelter |
| CIS | Component Information System |
| CIS | Contact Image Sensor |
| CIS | Criminal Investigative Service |