| Abbreviation | Definition |
|---|---|
| ISE | International Submarine Engineering |
| ISEA | In Service Engineering Agent |
| ISEC | Information Systems Engineering Command |
| ISEF | International Science and Engineering Fair |
| ISEIC | Information Systems Engineering Integration Center |
| ISEMP | Integrated Systems Engineering Management Plan |
| ISEMP | Integrated Systems Evaluation Management Plan |
| ISF | Integrated Support-Fielding |
| ISF | Intelligent Strong And Fast |
| ISF | Iraqi Security Forces |
| ISF | Iraqi Special Forces |
| ISG | Information Synchronization Group |
| ISG | Iraqi Survey Group |
| ISHM | Integrated System Health Monitoring |
| ISI | Insomnia Screening Index |
| ISI | Inter Systems Intelligence (Pakistan) |
| ISI | Inter-Service Intelligence |
| ISIL | Islamic State of Iraq and the Levant |
| ISIS | Integrated Signals Intelligence System |
| ISIS | Integrated Systems for Installation Support |