| Abbreviation | Definition |
|---|---|
| UDB | Update Buffer |
| UDF | Utility and Data Flow |
| UDL | Update Link |
| UDMH | Unsymmetrical Dimethylhydrazine |
| UDMH/H | Unsymmetrical Dimethylhydrazine Hydrazine Blend |
| UDOP | Ultrahigh Doppler |
| UDS | Universal Documentation System |
| UE | Upon Earth |
| UER | Unique Equipment Register |
| UFD | User File Directory |
| UFG | Unidentified Falling Groups |
| UHA | Ultra High Altitude |
| UHB | User Home Base |
| UHF | Ultrahigh Frequency |
| UHF | Ultra-High Frequency |
| UHQ | Ultra-High Quality |
| UHT | Ultra Heat Treated |
| UHT | Ultra Hot Temperature |
| UHV | Ultrahigh Vacuum |
| UHV | Ultra-High Vacuum |