|1.||[ adjective ] afflicted with or characteristic of mental derangement|
"was declared insane" "insane laughter"
|Related terms:||sane brainsick hebephrenic schizophrenic crackbrained paranoid maniacal crazed crazed psychopathic psychotic raving screw-loose lunatic mentally_ill maniclike non_compos_mentis fey balmy around_the_bend manic-depressive certifiable amuck irrational unreasonable|
|2.||[ adjective ] very foolish|
"harebrained ideas" "took insane risks behind the wheel" "a completely mad scheme to build a bridge between two mountains"