| Abbreviation | Definition |
|---|---|
| ULDB | Ultra-Long Duration Balloon |
| ULE | UltraLow Expansion |
| ULEP | Useful Life Extension Program |
| ULL | ULLage |
| ULO | Ultra Low Oxygen |
| ULO | Unmanned Launch Operations |
| ULT | Ultimate Load Test |
| ULT | Ultra- Low Temperature |
| ULVIM | ULtra-Violet Limb IMaging |
| ULX | Ultra- Luminous X-ray source |
| UMB | UMBilical |
| UMBC | UMBilical Cord |
| UMI | Urine Monitoring Investigation |
| UMO | Unmanned Orbital |
| UMS | Urine Monitoring System |
| UMV | Unmanned Work Vehicle System |
| UMV | Unrestricted Motion Vector |
| UMVF | Un-Manned Vertical Flight |
| UNBAL | Unbalance |
| UNDK | Undock |