subject matter subject index • subject substantive · · · Info · Definitions · Synonyms · Characters · · subject matter · · Text Common · · Latin · · Scripts 14 · · Length 4 · · Syllables Definitions · · · (noun) what a communication that is about something is about. Synonyms: message, content, subject matter, substance. · · Noun Definition 1 Synonyms · · · message · · Synonym 1 content · · Synonym 2 substance · · Synonym 3 Characters · · space U+0020 a latin small letter a U+0061 b latin small letter b U+0062 c latin small letter c U+0063 e latin small letter e U+0065 j latin small letter j U+006A m latin small letter m U+006D 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