insanity plea insanity • insanity-proof · · · Info · Definitions · Synonyms · Characters · · insanity plea · · Text Common · · Latin · · Scripts 13 · · Length 5 · · Syllables Definitions · · · (noun) (criminal law) a plea in which the defendant claims innocence due to mental incompetence at the time. Synonyms: insanity plea, plea of insanity. · · Noun Definition 1 Synonyms · · · plea of insanity · · Synonym 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 p latin small letter p U+0070 s latin small letter s U+0073 t latin small letter t U+0074 y latin small letter y U+0079