sicko

a person judged to be legally or medically insane some sicko kidnapped and murdered as many as a dozen young women Synonyms bug, crackbrain, crazy, fool, fruitcake, head case, loon, loony, maniac, nut, nutcase, nutter [British slang], psycho, psychopath, sickie, lunatic, wacko (also whacko)Related Words madman, madwoman; abnormal, deviant; manic-depressive, monomaniac, mythomaniac, neurotic, obsessive, obsessive-compulsive, paranoid, psychoneurotic, psychotic, schizo, schizoid, schizophrene, schizophrenic, sociopath; character, codger, crack, crackpot, crank, eccentric, fantastic (also fantastical), flake, kook, oddball, oddity, original, quiz, screwball, tyke (also tike) [chiefly British], weirdo, zany; case, patient