| Abbreviation | Definition |
|---|---|
| CISS | Centaur Integrated Support Structure |
| CIT | Critical Item Tag |
| CITE | Cargo Integration Test Equipment |
| CIU | Computer Interface Unit |
| CIU | Controller Interface Unit |
| CIV | Critical Ionization Velocity |
| CIVT | Cargo Interface Verification Test |
| CJC | Cold Junction Compensator |
| CK | ChecK |
| CK | Cylindrical Keplerian |
| CKAFS | Cape Kennedy Air Force Station (now called Cape Canaveral Air Force Station) |
| CKPT | Checkpoint |
| CKRA | Cape Kennedy Reference Atmosphere |
| CKT | CentiKelvin Thermometer |
| CL | CenterLine |
| CL | Close |
| CL | Closed Loop |
| CL | CLuster |
| CL | Coefficient of Lift |
| CL | Commonality List |