Psycho

Adjective

 * 1)  Psychotic, or otherwise insane.

Noun

 * 1)  A person who is psychotic or otherwise insane.
 * The loony bin up on the hill is full of psychos.
 * 1)  A person who acts in a bizarre or dangerous manner.
 * She complained that he was a psycho for driving at such a high speed in heavy traffic.
 * 1)  A class, at a college or university, in which psychology is taught.

Synonyms

 * freak, loony, nutcase, wacko
 * creep, freak, loose cannon, weirdo

Thesaurus
abnormal, bereft of reason, brainsick, catatoniac, certifiable case, crackbrained, cracked, crazed, crazy, daft, deluded, demented, deprived of reason, deranged, disoriented, distraught, flighty, hallucinated, insane, irrational, loco, lunatic, mad, maddened, manic, manic-depressive, mazed, mental, mental case, mentally deficient, meshuggah, moon-struck, non compos, non compos mentis, not all there, not right, odd, of unsound mind, off, paranoiac, paranoid, psychopath, psychopathic case, psychopathic personality, psychotic, queer, reasonless, schiz, schizo, schizoid, schizophrenic, schizy, senseless, sick, stark-mad, stark-staring mad, strange, tetched, touched, unbalanced, unhinged, unsane, unsettled, unsound, wandering, witless