| Abbreviation | Definition |
|---|---|
| IST | Institute for Simulation and Training |
| IST | Integrated System Test |
| IST | Interswitch Trunk |
| ISTA | Intelligence, Surveillance, and Target Acquisition |
| ISTC | Integrated System Test Capability |
| ISTEC | Information Systems Test and Evaluation Center |
| ISU | Independent Site Unit |
| ISU | Internal Airlift or Helicopter Slingable Container Unit |
| ISW | Infantry Support Weapon |
| ISYSCON | Information System Control |
| ISYSCON | Integrated System Control |
| IT | Induction Training |
| IT | Information Transport |
| IT | Innovative Tests |
| IT | Interoperability Testing |
| IT&E | Integration, Test, and Evaluation |
| ITA | Integrated Test Adapter |
| ITA | Intelligent Text Analyzer |
| ITA | International Telegraphic Alphabet |
| ITAAC | Inspection, Test, Analysis, and Acceptance Criteria |