| Acronym | Definition |
|---|
| FNSI➣Federazione Nazionale Stampa Italiana |
| FNSI➣Finding of No Significant Impact |
| FNSI➣Federación Nacional de Sindicatos Independientes (Spanish: National Federation of Independent Trade Unions; Mexico) |
| FNSI➣First Nations Statistical Institute (Canada) |
| FNSI➣Fiber Network Solutions, Inc. (internet provider) |