| Acronym | Meaning |
 | U/L | Uplink (UPLK Preferred) |
 | U/M | Unit Of Measure |
 | U/M | Unmanned |
 | U/M | Unscheduled Maintenance |
 | U/O | Used On |
 | U/V | Under Voltage |
 | U/W | Used With |
 | UA | Microampere |
 | UB | Upper Brace |
 | UB | UpUtility Bridge |
 | UBE | Universal Bus Exercisor |
 | UBIC | Universal Bus Interface Controller |
 | UC | Unsatisfactory Condition |
 | UCC | Universal Checkout Console |
 | UCD | Urine Collection Device |
 | UCN | Uniform Control Number |
 | UCPU | Urine Collection And Pretreatment Unit |
 | UCR | Unsatisfactory Condition Report |
 | UCS | Universal Control System |
 | UCS | UnUtilities Control System |
 | UCTA | Urine Collection Transfer Assembly |
 | UD | Update |
 | UDB | Update Buffer |
 | UDF | Utility And Data Flow |
 | UDL | Updata Link |
 | UDL | Update Link |
 | UDMH | Unsymmetrical Dimethylhydrazine |
 | UDMH/H | Unsymmetrical Dimethylhydrazine Hydrazine Blend |
 | UDOP | Ultrahigh Doppler |
 | UDS | Universal Documentation System |
 | UER | Unique Equipment Register |
 | UF | Microfarad |
 | UFD | User File Directory |
 | UG | Microgram |
 | UHF | Ultrahigh Frequency |
 | UHF | Ultrahigh Frequency |
 | UL | Underload |
 | UL | Unit Of Issue |
 | UL | Uplink |
 | UL | Upper Left (S-Band Antenna) |
 | UL | Upper Limit |
 | UL | User Interface |
 | ULA | Fairbanks |
 | ULL | Ullage |
 | ULO | Unmanned Launch Operations |
 | ULT | Ultimate |
 | UMB | Umbilical |
 | UMBC | Umbilical Cord Cable |
 | UMO | Unmanned Orbital |
 | UMVF | Unmanned Vertical Flight |