| Abbreviation | Definition |
|---|---|
| UC | Ubehebe Crater |
| UC | Unconfined Compression Test |
| UCG | Underground Compressed Gas |
| UEP | Upland Erosion Process |
| UGB | Upper Geyser Basin |
| UGC | Upper Gulf of California |
| UGPM | USIGS (United States Imagery and Geospatial System) Geospatial Production Management |
| UGS | Underground Gas Storage |
| UGS | Utah Geological Survey |
| UHB | UpHeaval Buckling |
| UIC | Underground Injection Control |
| UIS | Union Internationale de Speleologie |
| ULY | Ultra-fine-silty Loam, Super-active |
| ULY-A | Ultra-fine-silty Loam, Super-active, dark grayish brown |
| ULY-BA | Ultra-fine-silty Loam, Super-active, grayish brown |
| ULY-BC | Ultra-fine-silty Loam, Super-active, light gray |
| ULY-Bw | Ultra-fine-silty Loam, Super-active, light brownish gray |
| ULY-C | Ultra-fine-silty Loam, Super-active, pale brown |
| UMR-IWW | Upper Mississippi River- Illinois WaterWay |
| UMV | Upper Mantle Vessel |