| UA |
Unnumbered Acknowledgement |
| UBK |
Unblock |
| UBR |
User Bit Rate |
| U/C |
Up Converter |
| UDC |
Universal Data Classification |
| UDL |
Unified Data Library |
| UDMH |
Unsymmetrical DiMethyl Hydrazine |
| UDP |
User Datagram Protocol |
| UDTS |
Universal Data Transfer Service |
| UE |
User Equipment |
| UHF |
Ultra High Frequency |
| U/L |
Uplink |
| UL |
Uplink |
| UMC |
User Monitor Console |
| UMTS |
Universal Mobile Telecommunications System |
| UPS |
Uninterruptible Power Supply |
| USAT |
Ultra Small Aperture Terminal |
| USO |
Ultra Stable Oscillator |
| UST |
Universal Space Transponder |
| UST |
Unsuccessful Termination |
| UT |
Universal Time |
| UT |
User Terminal |
| UTC |
Coordinated Universal Time |
| UTC |
Universal Time Clock |
| UTP |
Unshielded Twisted Pair |
| UtU |
User to User |
| UUT |
Unit Under Test |
| UV |
Ultraviolet |
| UVN |
Ultraviolet – Visible – Near infrared |
| UW |
Unique Word |
