| Acronym | Definition |
|---|
| ISSU➣In Service Software Upgrade (system software upgrade without service interruption) |
| ISSU➣in Service Software Upgrades |
| ISSU➣Independent State Store Union (Pennsylvania) |
| ISSU➣International Student Support Unit (Australia) |
| ISSU➣Indigenous Schooling Support Unit (Australia) |
| ISSU➣Islamic Society of Stanford University |
| ISSU➣Idaho Steelhead and Salmon Unlimited (Idaho) |
| ISSU➣India Sunday School Union (est. 1876) |
| ISSU➣Integrated Support Services Unit (California) |
| ISSU➣Interface Signal Switching Unit (SQQ-28) |
| ISSU➣Irish Secondary Schools Union (Ireland) |