| | ULP | | unleaded petrol |
| | ULV | | Ultra Low Voltage |
| | uma | | Unlicensed Mobile Access |
| | UMD | | Universal Media Disc |
| | UML | | Unified Modeling Language |
| | UML | | Universal Modelling Language |
| | UMS | | Uniform Mark Scale |
| | UMS | | User Mode Schedulers |
| | UMTA | | urban mass transportation association |
| | UMTS | | Universal Mobile Telecommunications System |
| | UMTS | | Universal Mobile Telephone System |
| | un | | United Nations |
| | un | | unto |
| | 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 |
| | urgharo | | urgent help a reporter out |
| | URI | | universal resource indicator |
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