internal revenue internal respiration • internal revenue agent · · · Info · Definitions · Characters · · internal revenue · · Text Common · · Latin · · Scripts 16 · · Length 6 · · Syllables Definitions · · · (noun) government revenue from domestic sources (excluding customs). Synonyms: internal revenue. · · Noun Definition 1 Characters · · space U+0020 a latin small letter a U+0061 e latin small letter e U+0065 i latin small letter i U+0069 l latin small letter l U+006C n latin small letter n U+006E r latin small letter r U+0072 t latin small letter t U+0074 u latin small letter u U+0075 v latin small letter v U+0076