Synonyms for Loony (same or very similar meaning)
WordNet sense 1 (someone deranged and possibly dangerous):
crazy, weirdo, looneyWordNet sense 2 (informal or slang terms for mentally irregular):
balmy, batty, bonkers, buggy, cracked, crackers, daft, dotty, fruity, haywire, kooky, loco, loopy, nuts, nutty, wacky, barmy, kookie, whacky, around the bend, bats, round the bendWordNet sense 3 (afflicted with or characteristic of mental derangement):
insaneFrom the ODE community, based on WordNetadd/edit