| Abbreviation | Definition |
|---|---|
| ULS | User Level Security |
| UMA | Unlocking Mechanical Apparatus |
| UMD | Universal Media Disk |
| UMS | User Management System |
| UOWHF | Universal One-Way Hash Function |
| UPN | User Principal Name |
| UPUK | Universal Personal Unblocking Key |
| URA | Ultimate Revenge Attack |
| URA | User Role Assignment |
| URJ | Un-registration ReJection |
| URP | User Registration Protocol |
| URT | User Registration Tool |
| USHER | United States Higher Education Root |
| USM | User Session Management |
| USNM | User Name |
| USRT | Universal Synchronous Receiver/Transmitter |
| UTC | User Tracking Cookie |
| UTE | Unlimited Time to Enter |
| UTM | Unified Threat Management |
| UTMS | Unified Threat Management System |