1st-class mail 1st class • 1st earl attlee · · · Info · Definitions · Synonyms · Characters · · 1st-class mail · · Text Common · · Latin · · Scripts 14 · · Length 1 · · Syllables Definitions · · · (noun) mail that includes letters and postcards and packages sealed against inspection. Synonyms: first class, 1st class, first-class mail, 1st-class mail. · · Noun Definition 1 Synonyms · · · first class · · Synonym 1 1st class · · Synonym 2 first-class mail · · Synonym 3 Characters · · space U+0020 - hyphen-minus U+002D 1 digit one U+0031 a latin small letter a U+0061 c latin small letter c U+0063 i latin small letter i U+0069 l latin small letter l U+006C m latin small letter m U+006D s latin small letter s U+0073 t latin small letter t U+0074