| Abbreviation | Definition |
|---|---|
| GTR | Grand Trunk Railway |
| GTR | Great River Railroad - Rosedale-Bolivar County Port Commission |
| GTR | Great River Railroad (Rosedale-Bolivar County Port Commission) |
| GTRA | Golden Triangle Railroad |
| GTRR | Golden Triangle RailRoad |
| GTRR | Grand Trunk Railroad |
| GTTX | Trailer Train (TTX Corporation) |
| GTTX | TTX Company |
| GTW | Grand Trunk Western |
| GTW | Grand Trunk Western (Canadian National Railway) |
| GTW | Grand Trunk Western Railroad Incorporated |
| GTWQ | Grand Trunk Western (Canadian National Railway) |
| GTWQ | Grand Trunk Western Railroad Incorporated |
| GTZZ | GT Trucking |
| GTZZ | GT Trucking Incorporated |
| GU | Grafton and Upton Railroad |
| GU | Grafton and Upton Railroad Company |
| GUAX | Georgia Power |
| GUAX | Georgia Power Company |
| GUEX | General American Marks (GATX Corporation) |