insane

modif.

1. Deranged

   crazy, crazed, mad, wild, raging, frenzied, lunatic, schizophrenic, psychotic, psychopathic, psychoneurotic, paranoid, non compos mentis (Latin), maniacal, raving, demented, rabid, berserk, unbalanced, unhinged, act of one's mind, out of one's head, moonstruck, unsettled, mentally unsound, mentally diseased, sick, suffering from hallucinations, bereft of reason, daft, deluded, possessed, stark mad, having a devil, obsessed, disordered, touched, addlebrained, addlepated, addleheaded, nutty*, loony*, nuts*, schizo*, schizzy*, tetched*, balmy*, screwy*, loco*, off the wall*, wacko*, cuckoo*, bughouse*, crazy as a coot*, mad as a March hare*, gone*, derailed*, half-cocked*, haywire*, bats*, batty*, off the beam*, having bats in the belfry*, round the bend*, bonkers*, unglued*, nutty as a fruitcake*, off one's nut*, off one's rocker*, out of one's gourd*, dotty*, pixilated*, cracked*, having a few buttons missing*, one can short of a six-pack*, frothing at the mouth*, bananas*, not playing with a full deck*, out to lunch*, not all there*, wigged out*, off the deep end*; see also sick, violent 2, 4.

   Antonyms sane*, rational*, sensible. *

2. Utterly foolish

   madcap, daft, idiotic; see stupid 1.