Psycho is a slang term for someone who is mentally unstable or afflicted with a psychosis. Your best friend risks looking like a psycho if she keeps stalking her ex-boyfriend months after their breakup.

Psycho comes from the Greek word psykho, which means mental. Although the word has long been used as a prefix in words like psychologist, the pejorative term for a psychopath has only existed since the twentieth century. The word gained further notoriety after the 1960 release of Alfred Hitchcock's thriller, "Psycho." If you're always describing your boss as a psycho, you might want to think about looking for a new job.

Definitions of psycho
  1. noun
    a person afflicted with psychosis
    synonyms: psychotic, psychotic person
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    a person suffering from catalepsy
    paranoiac, paranoid
    a person afflicted with paranoia
    someone who is afflicted with schizophrenia
    type of:
    diseased person, sick person, sufferer
    a person suffering from an illness
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