| Acronym | Definition |
|---|
| NSIU➣Navigation Switching Interface Unit |
| NSIU➣Norges Svalbard- og Ishavs-Undersokelser |
| NSIU➣Nationwide Special Investigations Unit (Schaumburg, IL) |
| NSIU➣Navigation System Interface Unit |
| NSIU➣Non-Significant Industrial User |
| NSIU➣National Security Industry Union (UK) |