adj · noun · 5 senses · updated from the 2026-07-25 local source snapshot
Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.
Sound
Pronunciation
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Australian, UK:/ˈsaɪ̯.kəʊ̯/
Canada, US:/ˈsaɪ̯.koʊ̯/
Australia:Recorded audio is listed in the source snapshot.
rhymes with -aɪkəʊ
CMU ARPABET:S AY1 K OW0
Digits mark lexical stress: 1 primary, 2 secondary, 0 unstressed.
1
adj
Meaning 1
Psychotic, psychopathic, or (broadly) otherwise insane.
Definition source: English Wiktionary via Wiktextract
Usage: colloquial, derogatory
No example sentence was provided for this meaning.
Meaning relationships
Synonyms: none provided
Antonyms: none provided
2
noun
Meaning 2
A person who is psychotic, psychopathic, or (broadly) otherwise insane.
Definition source: English Wiktionary via Wiktextract
Usage: derogatory, slang
Examples
The loony bin up on the hill is full of psychos.
Meaning relationships
Synonyms: freak, loony, nutcase, wacko
Antonyms: none provided
3
noun
Meaning 3
A person who acts in a bizarre or dangerous manner.
Definition source: English Wiktionary via Wiktextract
Usage: broadly, derogatory, slang
Examples
She complained that he was a psycho for driving at such a high speed in heavy traffic.
Meaning relationships
Synonyms: creep, freak, loose cannon, weirdo
Antonyms: none provided
4
noun
Meaning 4
A class, at a college or university, in which psychology is taught.
Definition source: English Wiktionary via Wiktextract
Usage: informal, uncountable
Examples
I've got anthro, socio, lunch, and psycho.
Meaning relationships
Synonyms: none provided
Antonyms: none provided
5
noun
Meaning 5
a person afflicted with psychosis
Definition source: Princeton WordNet 3.0
No example sentence was provided for this meaning.