| Abbreviation | Definition |
|---|---|
| TOR | Time On Reference |
| TOT | Top Of Tree |
| TPC | Tactical Pilotage Charts |
| TPZ | Topaz |
| TRM | Thermal Remanent Magnetization |
| TRM | thermoremanent magnetization |
| TSA | Total Survey Area |
| TSU | tsunami |
| TT | Two Towers |
| TTE | Through The Earth |
| TTRD | Through Tubing Rotary Drilling |
| TTSN | Taiwan Telemetered Seismographic Network |
| TTSZ | Tomquist-Teisseyre Suture Zone |
| TVD | Tennessee Valley Divide |
| TVZ | Taupo Volcanic Zone |
| TWVF | Tuzo Wilson Volcanic Field |
| TXCY | Texas Clay Loam |
| UAC | Utah Avalanche Center |
| UB | Upper Boundary |
| UBSS | University of Bristol Spelæological Society |