| G | Ground |
| giga (1 000 000 000 = 109) |
| g | Force of gravity |
| Gram (0.001 kg) |
| G/A | Ground-to-air |
| G/G | Ground-to-ground |
| g/s | Ground speed |
| GA | General alert |
| General aviation |
| Ground attack |
| gal | Gallon (4.546 litres) |
| GALS | Globally asynchronous, locally synchronous |
| GAMTA | General Aviation Manufacturers & Traders Association |
| GAPAN | Guild of Air Pilots and Air Navigators |
| GAR | General assessment report |
| GARP | Global atmospheric research programme (WMO) |
| GASCO | General Aviation Safety Committee |
| GAT | General air traffic |
| Greenwich apparent time |
| GATCO | Guild of Air Traffic Control Officers |
| GATE | GARP Atlantic tropical experiment (WMO) |
| GATT | General Agreement on Tarrifs and Trade |
| Gb | Gigabyte (109 binary digits) |
| GC | Gas chromatography |
| Gyro compass |
| GCA | Ground-controlled approach |
| GCI | Ground-controlled interception |
| GCOS | Global climate observing system (of GOOS) |
| GCR | Group-coded recording |
| GCT | Greenwich civil time |
| GCU | Guidance and control unit |
| GD | Geared diesel |
| General duties |
| Ground defence |
| GDLP | Ground data link processor |
| GDN | Government data network |
| GDP | General defence plan |
| Gross domestic product |
| GDU | Graphical display unit |
| GE | Ground environment |
| GEM | Ground-effect machine |
| gen | General |
| Generator (power) |
| geo | Geographic |
| GEODSS | Ground-based electro-optical deep surveillance system |
| georef | Geographic reference system |
| GESAMP | Group of experts on scientific aspects of marine pollution |
| GFA | Gun fire area |
| GFE | Government-furnished equipment |
| GFI | Government-furnished information |
| GFM | Government-furnished materiel |
| GFR | Gap-filling radar |
| GHA | Greenwich hour angle (nav) |
| GHAMS | Greenwich hour angle mean sun (nav) |
| GHATS | Greenwich hour angle true sun (nav) |
| GHz | Gigahertz |
| GIGO | Garbage in, garbage out |
| GIPME | Global investigation of pollution in the marine environment (of GOOS) |
| GIS | Geographic information system |
| GKM | General key management (communications) |
| GLCM | Ground-launched cruise missile |
| GLO | Ground liaison officer |
| glonass | Global navigation satellite system |
| GLOSS | Global sea level observing system |
| GM | Guided missile |
| GMC | Ground movement control |
| GMDSS | Global maritime distress and safety system |
| GMP | Ground movement planner |
| GMS | Geostationary meteorological satellite |
| gms | Gram-metre-second system of measurement |
| GMT | Greenwich mean time |
| GNC | Global navigation chart |
| gnd | Ground |
| GNP | Gross national product |
| GNR | General nuclear response |
| GNS | Global navigation system |
| GNSS | Global navigation satellite service |
| Global navigation satellite system |
| GOC | General officer commanding |
| GOOS | Global Ocean Observing System |
| GOS | Global observation service (WMO) |
| GP | General purpose |
| Glide path |
| GPI | Glide path indicator |
| GPIB | General-purpose interface bus (electronics) |
| GPMG | General-purpose machine gun |
| GPRS | General packet radio system |
| GPS | Global positioning system (nav) |
| GPTN | General-purpose telecommunications network |
| GPU | Ground power unit (aircraft) |
| GPWC | Ground proximity warning computer |
| GPWS | Ground proximity warning system (for civil airliners) |
| GQA | Government quality assurance |
| GRC | Glassfibre-reinforced concrete |
| GRE | Ground replay equipment (data record) |
| grobat | Ground order of battle |
| GRP | Glassfibre-reinforced plastics |
| GRT | Gross registered tonnage |
| GS | Glide slope |
| Ground speed |
| GSB | General support bridge |
| GSE | Ground support equipment (aviation) |
| GSM | Global standard on mobiles (communications) |
| Global system for mobile (telephones) |
| Group standard mobile (telephone) |
| GSO | Geostationary orbit |
| GSP | General strike plan |
| GT | Gas turbine |
| General transport |
| Gross tonnage |
| GT-E | Gas turbo-electric |
| GTE | Ground test equipment |
| GTOS | Global terrestial observing system |
| GTS | Gas turbine starter |
| GTSP | Global temperature salinity project (of IGOSS) |
| GTV | Gas turbine vessel |
| GTW | Gross tare weight |
| Gross train weight |
| GUI | Graphics user interface (computer) |
| GVW | Gross vehicle weight |
| GW | Guided weapon |
| GWS | Guided weapon system |
| GZ | Ground zero |
