| Abbreviation | Definition |
|---|---|
| UR | Unanimity Rule |
| UR | Underground Railroad |
| UR | Update Recalls |
| URA | Unemployment Relief Act |
| URAA | Uruguay Round Agreements Act of 1994 |
| URC | Under Red Caps |
| URG | Urgent |
| URM | Under Represented Minority |
| URMCC | Utah Reclamation Mitigation and Conservation Commission |
| URN | Uniform Resource Name |
| URT | Utilities Review Team |
| US | Uncle Sam |
| USACE | United States Army Corps of Engineers |
| USAFA | United States Air Force Academy |
| USAID | The United States Agency for International Development (USAID) |
| USAISR | United States Army Institute of Surgical Research |
| USAP | United States Antarctic Program (NSF) |
| USARP | United States Antarctic Program |
| USAS | United States Antarctic Service |
| USASI | United States of America Standard Institute |