dead letter dead-lette • dead-letter · · · Info · Definitions · Synonyms · Characters · · dead letter · · Text Common · · Latin · · Scripts 11 · · Length 3 · · Syllables Definitions · · · (noun) the state of something that has outlived its relevance. Synonyms: dead letter, non-issue. · · Noun Definition 1 (noun) mail that can neither be delivered nor returned. Synonyms: dead letter, dead mail. · · Noun Definition 2 Synonyms · · · non-issue · · Synonym 1 dead mail · · Synonym 2 Characters · · space U+0020 a latin small letter a U+0061 d latin small letter d U+0064 e latin small letter e U+0065 l latin small letter l U+006C r latin small letter r U+0072 t latin small letter t U+0074