# psycho

/ˈsaɪkoʊ/ (US) · /sˈaɪkəʊ/ (UK)

Source: https://englishreference.com/word/psycho
Updated: 2026-06-20

## Senses

### 1. a dangerous or unstable person

noun · CEFR B2 · Informal · Slang

a person who acts in a very strange, violent, or scary way.

For teachers: a person perceived as being mentally unstable, aggressive, or dangerously unpredictable.

- Stay away from him; he acts like a total psycho when he gets angry.
- The tabloid media was quick to label the suspect a psycho, focusing on his erratic behaviour rather than the underlying social causes of the incident.

Teaching tip: This word is often considered offensive or insensitive because it trivialises mental health issues; use it with caution.

### 2. crazy or scary

adjective · CEFR C1 · Informal · Slang

behaving in a way that is crazy, scary, or out of control.

For teachers: exhibiting behaviour that is perceived as psychotic, irrational, or dangerously unstable.

- She has a psycho ex-boyfriend who keeps calling her from different numbers.
- His psycho reaction to a minor traffic disagreement left the other drivers in the car park feeling genuinely threatened.

### 3. psychology class

noun · CEFR C1 · Informal · American English

a short way of saying 'psychology' when talking about a school or university subject.

For teachers: an informal, uncountable shorthand for the academic discipline or a specific course in psychology.

- I have my psycho 101 exam tomorrow morning, so I need to study tonight.
- Most students in the psycho department found the introductory lectures on behavioural patterns surprisingly challenging.

Usage: This sense is typically uncountable and used primarily in student contexts.

## Examples

- He started acting like a total psycho during the argument.
- The neighbors thought he was a psycho because he would scream at his lawn in the middle of the night.
- While the film portrays the antagonist as a typical Hollywood psycho, modern critics argue the characterization relies on outdated and harmful tropes regarding mental health.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.