| Term | Definition | Contributor | Modified |
|---|---|---|---|
| Underground railroad | No definition provided | Christopher Rauch | 2023.12.01 |
| Underground railroads | No definition provided | Christopher Rauch | 2023.12.01 |
| underground water | No definition provided | Ryan McGranaghan | 2023.04.16 |
| Underground water | No definition provided | Christopher Rauch | 2023.12.01 |
| Undermelting | The melting from below of any floating ice. | GCW Glossary | 2023.03.27 |
| Underpinning | No definition provided | Christopher Rauch | 2023.12.01 |
| undersaturated | No definition provided | Ryan McGranaghan | 2023.04.16 |
| Understanding | No definition provided | Christopher Rauch | 2023.12.01 |
| Undertakers and undertaking | No definition provided | Christopher Rauch | 2023.12.01 |
| Undertakers and undertaking--Directories | No definition provided | Christopher Rauch | 2023.12.01 |
| underwater | No definition provided | Ryan McGranaghan | 2023.04.16 |
| Underwear | No definition provided | Christopher Rauch | 2023.12.01 |
| Underwriting | No definition provided | Christopher Rauch | 2023.12.01 |
| undesirable | No definition provided | Ryan McGranaghan | 2023.04.16 |
| Undine (Minor planet) | No definition provided | Christopher Rauch | 2023.12.01 |
| Undine (Ship) | No definition provided | Christopher Rauch | 2023.12.01 |
| undirected graph | No definition provided | Ryan McGranaghan | 2023.04.16 |
| Undulant fever | No definition provided | Christopher Rauch | 2023.12.01 |
| undulation | No definition provided | Ryan McGranaghan | 2023.04.16 |
| Undulatory theory | No definition provided | Christopher Rauch | 2023.12.01 |