| Abbreviation | Definition |
|---|---|
| NICI | National Information And Communication Initiative |
| NICS | National Instant Criminal Background Check System |
| NID | National Investigation Department |
| NIDCD | National Institute on Deafness and Other Communication Disorders (NIH) |
| NIDDK | National Institute of Diabetes and Digestive and Kidney Disease |
| NIDDKD | National Institute of Diabetes and Digestive and Kidney Diseases |
| NIE | National Intelligence Estimate |
| NIEM | National Information Exchange Model |
| NIF | Nuclear Insanity Forever |
| NIFA | National Institute of Food and Agriculture |
| NIGP | National Institute of Government Purchasing |
| NIH | Not Invented Here |
| NIHC | National Health Information Center |
| NIJ | National Institute of Justice |
| NIM | National Institute of Management |
| NIM | Non Important Message |
| NIMBY | Not Intimidated Much By Yelling |
| NIMO | National Incident Management Organization |
| NIN | National Insurance Number |
| NIO | New Imperial Order |