| Acronym | Meaning |
| GEASIC | Gradient-expansion Approxn. Self-interaction Correction (functional |
| GECSC | Generalized Exponential Cosine Screened Coulomb (potential) |
| GEENET | Global Environmental Epidemiology Network |
| GEF | Guanine Nucleotide Exchange Factor |
| GEH | Generalized Effective Hamiltonian |
| GEIA | Global Emissions Inventory Assessment |
| GEIS | Generic Environmental Impact Statement |
| GEK | Geomagnetic Electrokinetograph |
| GEKT | Generalized Extended Koopmans Theorem |
| GEM | Gas Electron Multiplier |
| GEM | Gene Expression Microarray |
| GEM | Genetically Engineered Microorganism |
| GEMAP | Geocoded Emission Modeling And Projection |
| GEMI | Global Environmental Management Initiative |
| GEML | Gene Expression Markup Language |
| GEMMA | Gas-phase Electrophoretic Mobility Molecular Analysis |
| GEMS | Global Environmental Monitoring Systems |
| GEMS | Graphical Exposure Modeling System |
| GEMS | General Energy And Material Balance System [model] |
| GENESIS | Global Environmental And Ecological Simulation Of Interactive Systems |
| GEO | Gene Expression Omnibus |
| GEO | Geostationary Earth Orbit |
| GEOS | General Earthquake Observation System |
| GEOS | Goddard Earth Observing System |
| GEOSECS | Geochemical Ocean Sections |
| GEP | Good Engineering Practice |
| GERD | Gastroesophageal Reflux Disease |
| GERM | Geochem. Earth Ref. Model |
| GESAMP | Group Of Experts On The Scientific Aspects Of Marine Pollution |
| GETE | Global Environmental Technology Enterprise |
| GEWEX | Global Energy And Water Cycle Experiment |
| GEXRF | Grazing-emission X-ray Fluorescence |
| GEXRS | Grazing-exit X-ray Spectrometry |
| GFA | Glass-forming Ability |
| GFAA | Graphite Furnace Atomic Absorption |
| GFAAS | Graphite Furnace Atomic Absorption Spectroscopy |
| GFAP | Glial Fibrillary Acidic Protein |
| GFC | Gel Filtration Chromatography |
| GFCI | Ground Fault Circuit Interrupter |
| GFCM | Green-function Cellular Method |
| GFCR | Gas Filter Correlation Radiometry |
| GFCS | Gas Filter Correlation Spectroscopy |
| GFDL | Geophysical Fluid Dynamics Laboratory |
| GFEMO | Generalized Free Electron Molecular Orbital |
| GFF | Green Function Formalism |
| GFF | Glass Fiber Filter |
| GFFF | Gravitational Field-flow Fractionation |
| GFIS | Gas Field Ion Source |
| GFMC | Green Function Monte Carlo (quantum Method) |
| GFMT | Green Function Muffin Tin (method In Electronic Structure Study) |