adj. 25B6; adjective
she was declared insane : MENTALLY ILL, mentally disordered, of unsound mind, certifiable; psychotic, schizophrenic; mad, deranged, demented, out of one's mind, non compos mentis, sick in the head, unhinged, unbalanced, unstable, disturbed, crazed; informal crazy, (stark) raving mad, not all there, bonkers, cracked, batty, cuckoo, loony, loopy, nuts, screwy, bananas, wacko, off one's rocker, off one's head, round the bend; Brit. informal crackers, barmy, barking (mad), off one's trolley, round the twist, not the full shilling; N. Amer. informal buggy, nutso, out of one's tree; Austral./NZ informal bushed.
an insane suggestion : FOOLISH, idiotic, stupid, silly, senseless, nonsensical, absurd, ridiculous, ludicrous, preposterous, fatuous, inane, asinine, hare-brained, half-baked; impracticable, implausible, irrational, illogical; informal crazy, mad, cock-eyed; Brit. informal daft, barmy.
sensible, calm.