supertax supertartrate • supertaxation · · · Info · Definitions · Synonyms · Characters · · supertax · · Text Latin · · Script 8 · · Length 3 · · Syllables Definitions · · · (noun) an additional tax on certain kinds of income that has already been taxed. Synonyms: surtax. · · Noun Definition 1 Synonyms · · · surtax · · Synonym 1 Characters · · a latin small letter a U+0061 e latin small letter e U+0065 p latin small letter p U+0070 r latin small letter r U+0072 s latin small letter s U+0073 t latin small letter t U+0074 u latin small letter u U+0075 x latin small letter x U+0078