| Abbreviation | Definition |
|---|---|
| CMS | Centers for Medicare Medicaid Services (prev. HCFA) |
| CMS | Centers for Medicare & Medicaid Services (prev. HCFA) |
| CMS | Centers for Medicare and Medicaid Services |
| CMS | Centers for Medicare and Medicaid Services (DHHS) (formerly HCFA) |
| CMS | Centres for Medicare & Medicaid Services |
| CMS | Correctional Medical Services |
| CMSAF | Chief Master Sergeant of the Air Force |
| CMSgt | CMSgt Chief Master Sergeant - USAF |
| CN | Community Nurses |
| CNI | Critical National Infrastructure |
| CNIDR | Center for Networked Information |
| CNP | Comprehensive National Power |
| CNST | The Center for Nanoscale Science and Technology |
| CNTPO | Counter-Narcoterrorism Technology Program Office (U.S. Department of Defense) |
| CNTRY | CouNTRY |
| CO | Capital Offence |
| COB | Continuous Open Bidding |
| COB | Coordination Of Benefits |
| COBA | Coordination of Benefits Agreement (Centers for Medicare & Medicaid Services) |
| COBR | Cabinet Office Briefing Room |