| Abbreviation | Definition |
|---|---|
| IG | Information Gain |
| IG | Inspector General |
| IGCE | Independent Government Cost Estimate |
| IGE | Independent Government Estimate |
| IGES | Initial Graphics Exchange Specification |
| IGI | I'm Going In |
| IGI | Institute for Geotactical Intelligence |
| IGI&S | (The Army's) Installation Geographic Information & Services |
| IGL | Intelligence Gain/loss |
| IGM | Improved Guided Munitions |
| IGMP | Internet Group Management Protocol |
| IGN | Ignite |
| IGO | I am leaving the scene |
| IGO | Intergovernmental Organization |
| IGOSS | Industry/Government Open Systems Specification |
| IGRV | Improved GUARDRAIL V |
| IGRVARF | Improved GUARDRAIL V Airborne Relay Facility |
| IGRV-IPF | IGRV-Integrated Processing Facility |
| IGRV-IPF | Improved Guard Rail V - Integrated Processing Facility |
| IGS | Instrument Guiding System |