| Acronym | Meaning |
| NMSG | NATO Modelling And Simulation Group |
| BTIS | Battlefield Target Identification System |
| GRB | Gamma-Ray Burst |
| GRAS | Generally Regarded As Safe (FDA List) |
| GRC | Greece (ISO 3166 Trigram) |
| GR | Greece (FIPS 10-4 Country Code; ISO 3166 Digram) - Hail (METAR Code) |
| SLR | Single-Lens Reflex (camera) |
| DSN | Deep Space Network |
| IMRI | Industrial Membrane Research Institute - Information Management Research Institute - Institut Pour Le Management De La Recherche Et De L?innovation (French |
| AJ | Attojoule |