| Abbreviation | Definition |
|---|---|
| GLY | GLYcol |
| GM | Gaseous Mixture |
| GM | Geometric Mean |
| GMAL | General Electric Macro Assembly Language |
| GMAN | General Maneuver |
| GMBL | GiMBaL |
| GMCL | Ground Measurements Command List |
| GME | Gyro Management Electronics |
| G-MEM | General MEMory |
| GMES | Global Monitoring for Environment and Security |
| GMIL | Government, Merritt IsLand, Florida Spaceflight Tracking and Data Network station |
| GML | General Measurement Loop |
| GMML | Ground Master Measurements List |
| GMN | Gorman, California TACAN Station |
| GMT | Greenwich Mean Time (replaced by UT in 1928, then UTC in 1960) |
| GMU | Gyro Mechanical Unit |
| GN | GaiN |
| GN | Ground Network |
| GN&C | Guidance, Navigation, and Control |
| GN2 | Gaseous Nitrogen |