fo f number • Fo · · · Info · Definitions · Synonyms · Characters · · fo · · Text Latin · · Script 2 · · Length 1 · · Syllables Definitions · · · (noun) an officer holding the rank of major or lieutenant colonel or colonel. Synonyms: field-grade officer, field officer, FO. · · Noun Definition 1 Synonyms · · · field-grade officer · · Synonym 1 field officer · · Synonym 2 Characters · · f latin small letter f U+0066 o latin small letter o U+006F