| Acronym | Definition |
|---|
| FESI | Free Ecma Script Interpreter |
| FESI | Fonds d'Entraide et de Solidarité Internationale (French: Assistance Fund and International Solidarity) |
| FESI | Federation of the European Sporting Goods Industry |
| FESI | Fédération Européenne des Syndicats d'Entreprises d'Isolation (French: European Federation of Trade Unions Business Insulation) |
| FESI | Federacion Espanola de Sociedades de Informatica (Spain) |
| FESI | Field-Enhanced Sample Injection |
| FESI | Forum for Engineering Structural Integrity (UK) |
| FESI | Family Economic Security Initiative (Californians for Economic Security) |