Noun

• S: (n) crazy, loony, looney, nutcase, weirdo (someone deranged and possibly dangerous)
• domain usage
• direct hypernym / inherited hypernym / sister term

Adjective

• S: (adj) balmy, barmy, bats, batty, bonkers, buggy, cracked, crackers, daft, dotty, fruity, haywire, kooky, kookie, loco, loony, loopy, nuts, nutty, round the bend, around the bend, wacky, whacky (informal or slang terms for mentally irregular) "it used to drive my husband balmy"