2. Abbreviation. fidelity, as in ''sound hi-fi'' ¹
3. Abbreviation. abbr. for the Latin fidelis - as in ''Semper fi'' ¹
4. Abbreviation. fiction ¹
5. Noun. (music) The solfeggio syllable used to indicate the sharp of the fourth note of a major scale. ¹
6. Abbreviation. (computer science) The end if program instruction, usually as shorthand. ¹
¹ Source: wiktionary.com