| Abbreviation | Definition |
|---|---|
| ULC | Universal Line Card |
| ULL | Unbundled Local Loop |
| ULLS | Unconditioned Local Loop Service |
| ULQ | User Level Quality |
| UMA | Unlicensed Mobile Access |
| UMATS | University of Maryland Academic Telecommunication System |
| UMC | Ukrainian Mobile Communications |
| UMS | Unified Messaging Service |
| UMTS | Unified Mobile Telecommunication System |
| UMTS | Universal Mobile Telecom Surfwax |
| UMTS | Universal Mobile Telecommunication Services |
| UMTS | Universal Mobile Telecommunication System |
| UMTS | Universal Mobile Telecommunications Service |
| UMTS | Universal Mobile Telecommunications Services |
| UMTS | Universal Mobile Telecommunications Standard |
| UMTS | Universal Mobile Telecommunications System |
| UNI | User Network Interface |
| UNICODE | UNIversal trunk - out-of-service CODE |
| UNL | UNListed |
| UNLD | UNlimited Long Distance |