psycho
noun
a psychopathic or psychotic person.
psycho
1 American
[sahy-koh]
/ ˈsaɪ koʊ /
noun
-
psychos
plural
-
a psychopathic or psychotic person.
-
a crazy or mentally unstable person.
adjective
-
psychopathic or psychotic.
-
crazy; mentally unstable.
psycho-
2
American
psycho-
1
British
combining form
psycho
2
British
/ ˈsaɪkəʊ /
noun
Usage
What does psycho- mean? Psycho- is a combining form used like a prefix meaning either “psyche” or "psychological." Psyche denotes "the human soul, spirit, or mind," while psychological is a related yet distinct term that means "pertaining to psychology, the science of the mind or of mental states." Psycho- is often used in medical and technical terms, especially in psychology. Psycho- comes from Greek psȳchḗ, meaning “breath, spirit, soul, mind.” For more on the meaning of this word in Ancient Greek mythology, read our entry for psyche. The word psyche is at the root of the term psychedelic, which refers to the effect of hallucinogenic drugs. What are variants of psycho-?When combined with words or word elements that begin with a vowel, psycho- becomes psych-, as in psychiatry. Want to know more? Read our Words That Use article on psych-.
Other Word Forms
Noun Inflected Forms
Etymology
Origin of psycho1
First recorded in 1935–40; by shortening
Origin of psycho-2
< Greek, combining form of psȳchḗ breath, spirit, soul, mind; akin to psȳ́chein to blow ( see psykter)
Explanation
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.
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
“Is she right? Is she wrong? Is she psycho? Is she sane? Is she brilliant? Is she all of those things? Or none of them? You can’t pin her down,” Jonas explains.
From Los Angeles Times ● Feb. 26, 2026
"I am just looking at her and thinking she could be sweet but a psycho, like that would be brilliant," Rachel told the other traitors.
From BBC ● Jan. 6, 2026
“No! Bad, psycho governor! No! Sit down! Bad! Stay! Stay away from dogs!”
From New York Times ● Apr. 30, 2024
“They go psycho on you, because they’re all psychopaths. They’re arrogant psychopaths with God complexes because our society has moved people to idolize doctors.”
From Seattle Times ● Jul. 19, 2023
I mean, we weren’t best friends or anything, and he was mostly a psycho who I was definitely gonna part ways with the second we got to Mexico, but still.
From "We Were Here" by Matt De La Peña
But as a treatment adjunct, psycho- oncology is creeping into the mainstream.
From Time Magazine Archive
Some were psycho- statistical: the inherent uncertainty of life had engendered an irrationality among economic decision makers.
From Time Magazine Archive
That whole business with the psychiatrist that dragged on forever. 10TH JUROR: NOW don’t start with all that phoney psycho- whatever-you-call-it-stuff.
From "Twelve Angry Men" by Reginald Rose
These terms are familiar to him, but the sight of a phrase like "psycho- physical parallelism" rather daunts him.
From Bergson and His Philosophy by John Alexander Gunn
The Lecture given at the International Congress at Geneva, formerly printed in the Revue de metaphysique et de morale as "Le Paralogisme psycho- physiologique."
From Bergson and His Philosophy by John Alexander Gunn
She remembers feeling "upset" and "lonely" after someone shared one of her posts with the caption: "The psychos are at it again."
From BBC ● Feb. 27, 2023
“We need a few more psychos on this team,” said one player.
From Seattle Times ● Mar. 17, 2022
Nesbo’s Norway, like Stieg Larsson’s Sweden, is populated with creeps and psychos of the sort that turn up here in much greater abundance.
From New York Times ● Nov. 6, 2020
The audacious premise: Even a bunch of notorious psychos can have a good moment.
From Los Angeles Times ● Feb. 4, 2020
“I want to be as close as possible! Run along its edges so we know exactly where we are! And maybe lose those psychos while we’re at it!”
From "The Kill Order (Maze Runner, Book Four; Origin)" by James Dashner
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
