| Abbreviation | Definition |
|---|---|
| TYX | National Weather Service, Montague, New York, radar |
| TZC | Time Zone Converter |
| TZD | True Zenith Distance |
| U | Uncertain |
| UAAS | Upper Air Atmospheric Sounding |
| UAM | Urban Airshed Model |
| UAP | Unidentified Aerial Phenomena |
| UAPTF | Unidentified Aerial Phenomena Task Force |
| UAR | Upper Atmosphere Research |
| UATD | Urban Area Transport and Dispersion |
| UAV | Unmanned Aerial Vehicle |
| UGF | Under-Ground Facility |
| UGS | Unattended Ground Sensor |
| UHA | Ultra High Altitude |
| UHI | Ultra- High Intensity |
| UHM | Undersea & Hyperbaric Medicine Society |
| UKMET | United Kingdom's Meteorological Office |
| UKV | United Kingdom Variable-resolution weather forecasting system |
| ULF | Ultra Low Frequency |
| ULI | Upper Layer Indication |