| U5MR | Under 5 Mortality Rate 
| Others |
| U75 | Jackass Aeropark, Amargosa Valley, Nevada USA (closed 2004)
| Others |
| U8 | You Ate
| Others |
| UA | A Unit Aide
| Others |
| uA | microAmpere
| Others |
| UA | Ukraine According
| Others |
| UA | Ultimate Adventure
| Others |
| UA | Ultimate Ancestor
| Others |
| UA | Ultimate Armor
| Others |
| UA | Ultimate Armour
| Others |
| UA | Ultimate Assasins
| Others |
| UA | Ultimate Assassins
| Others |
| UA | Ultrasonic Arteriography
| Others |
| UA | Umbilical Artery
| Others |
| UA | Unanieme Alcoholisten
| Others |
| UA | Unauthorised Authentics
| Others |
| UA | UnAuthorized
| Others |
| UA | Unauthorized Absence
| Others |
| UA | Unauthorized Authentic
| Others |
| UA | Unconditional Annihilation
| Others |
| UA | Under Anesthesia
| Others |
| UA | Under Armor
| Others |
| UA | Under Armored
| Others |
| UA | Undercover Agent
| Others |
| UA | Undercover Aura
| Others |
| UA | Undergraduate Assistant
| Others |
| UA | Undergraduate Association
| Others |
| UA | Undergraduate Assosciation
| Others |
| UA | Underground Access
| Others |
| UA | Underground Area
| Others |
| UA | Underlying Asset
| Others |
| UA | Underwriters Association
| Others |
| UA | Unholy Alliance
| Others |
| UA | Unicystic Ameloblastoma
| Others |
| UA | Unidad Alavesa
| Others |
| UA | Unified Agenda
| Others |
| UA | Unified Architecture
| Others |
| UA | Uniform Asymptotic
| Others |
| UA | Union Avoidance
| Others |
| UA | Unique Address
| Others |
| UA | Unit Administration
| Others |
| UA | Unit Attack
| Others |
| UA | Unit Authorization
| Others |
| UA | Unit Availability
| Others |
| UA | Unit of Account
| Others |
| UA | Unitary Authority
| Others |
| UA | Unitary Authority (Unitary Council)
| Others |
| UA | United Airlines
| Others |
| UA | United Almighty
| Others |
| UA | United America
| Others |