| | UMTS | | Universal Mobile Telephone System |
| | un | | United Nations |
| | UNC | | Uniform Naming Convention |
| | UNESCO | | United Nations Education and Scientific Organization |
| | UNESCO | | United Nations educational, scientific and cultural organisation |
| | UNICEF | | United Nations International Children's Emergency Fund |
| | UNT | | Undergraduate Navigator Training Navigator training |
| | UNT | | Unit Next Time |
| | UOINDIC | | Unless Otherwise INDICated |
| | UOM | | Unit of Measure |
| | UPC | | Universal Product Code |
| | UPOA | | Unsolicited Piece Of Advice |
| | UPOC | | universal point of contact |
| | UPS | | Uninterruptible Power Supply |
| | UPS | | Uninterupted Power Supply |
| | UPS | | Unnatural Pile of Sticks |
| | UPVC | | Unplasticised Poly Vinyl Chloride |
| | URI | | universal resource indicator |
| | US | | United States |
| | USA | | United States of America |
| | USB | | Uniform Serial Bus |
| | USB | | Universal Serial Bus |
| | USLD | | ultra low sulfur diesel |
| | USMC | | United States Marine Corps |
| | USMC | | US Marine Corps |
| | USP | | Unique Selling Position |
| | USP | | Unique Selling Proposition |
| | USPTO | | United States Patent and Trademark Office |
| | usrda | | United States Recommended Daily Allowances |
| | USSD | | unstructured supplementary service data |
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