having or showing a very abnormal or sick state of mind the movie's villain was a just a clichéd axe-wielding nutcase with a maniacal laugh Synonyms balmy, barmy [chiefly British], bats, batty, bedlam, bonkers, brainsick, bughouse [slang], certifiable, crackbrained, cracked, crackers, crackpot, cranky [dialect], crazed, crazy, cuckoo, daffy, daft, ...