| Acronym | Meaning |
| CAPS | Cassini Plasma Spectrometer |
| CAPTEX | Cross-Appalachian Tracer Experiment |
| CAR | Central African Republic |
| CARA | Center For Astrophysical Research In Antarctica |
| CARB | California Air Resources Board |
| CARD | Citizens Against Radioactive Dumping |
| CARL | Colorado Alliance Of Research Libraries |
| CARP | Carpenter Research Project |
| CARP | Colorado-Amudarya Rivers Project |
| CARS | Coherent Anti-Stokes Raman Spectroscopy |
| CARSS | Center For Atmospheric And Remote Sounding Studies |
| CART | Cloud And Radiation Testbed |
| CAS | Cooperative Application Satellite |
| CAS | Committee On Atmospheric Sciences |
| CAS | Commission For Atmospheric Science |
| CAS | Climate Analysis Section |
| CAS | Center For Automotive Safety |
| CAS | Chemical Abstract Service |
| CASAC | Clean Air Scientific Advisory Committee |
| CASC | Coalition For Academic Supercomputer Centers |
| CASE | Computer Aided Software Engineering |
| CASES | Cooperative Atmosphere Surface Exchange Study |
| CASH | Commercial Aviation Sensing Humidity Program |
| CASH | Commercial Aviation Sensing Of Humidity |
| CASI | Canadian Aerospace Institute |
| CASP | Canadian Atlantic Storms Project (or Program) |
| CASS | Computer-Assisted Surveillance System |
| CAST | Council For Agricultural Science And Technology |
| CAST | Chinese Academy Of Space Technology |
| CASW | Council For The Advancement Of Science Writing |
| CAT | Clear Air Turbulence |
| CAT | Coordinated Analysis Of The Thermosphere |
| CATI | Colorado Advanced Technology Institute |
| CB | Cumulonimbus |
| CB | Meteorological Symbol |
| CBASSE | Commission On Behavioral & Social Sciences And Education |
| CBB | Contract Budget Baseline |
| CBERS | China-Brazil Earth Resources Satellite |
| CBL | Convective Boundary Layer |
| CBL | Computer-based Learning |
| CBLCBNM | Central Bureau Of Nuclear Measurements |
| CBO | Carrier Balloon/Omegasonde |
| CBO | Congressional Budget Office |
| CBRS | Coastal Barrier Resources System |
| CBSS | Change Board Support System |
| CBT | Computer Based Training |
| CCAA | Canadian Clean Air Act |
| CCAB | CGD Computing Advisory Board |
| CCAR | Colorado Center For Astrodynamics Research |
| CCARS | Computer Controlled Automatic Rain Sampler |