| Abbreviation | Definition |
|---|---|
| UIN | Unit Identification Number |
| UI-NEW | Unit of Issue - New |
| UIR | User Interface Requirement |
| UIRV | Unique Interswitch Rekeying Variable |
| UIS | Unit Identification System |
| UIS | User Interface Specification |
| UISL | User Interface Specification Language |
| UISS | Unmanned Influence Sweep System |
| UJC | Urgency Justification Code |
| UJP | Urban Jungle Pack |
| UJT | Underwater Job Training |
| UJTL | Universal Joint Task List |
| UK | United Kingdom |
| UK(I) | United Kingdom and Ireland |
| UKM | Universal Killing Machine |
| UKN | United Kingdom Navy |
| UKO | United Kingdom Operations |
| UKSAC | University of Kentucky Salvation Army Clinic |
| UL | Ultra Loader |
| UL | Unit Level |