# lunatic

/ˈɫunəˌtɪk/ (US) · /lˈuːnətˌɪk/ (UK)

Source: https://englishreference.com/word/lunatic
Updated: 2026-08-08

## Senses

### 1. a reckless person

noun · CEFR C1 · Informal

someone who behaves in a very silly, dangerous, or crazy way.

For teachers: a person who acts in a reckless, irrational, or extremely foolish manner. While originally a clinical term, it is now used as a harsh informal pejorative.

- He was driving like a lunatic and almost caused a serious accident.
- The CEO was described as a lunatic by former employees who witnessed his increasingly erratic and high-risk decision-making.

Usage: Often used in the phrase 'drive like a lunatic' to describe dangerous behavior on the road.

Teaching tip: This word is considered offensive if used to describe someone with actual mental health issues; it is best reserved for describing reckless behavior.

### 2. extremely foolish

adjective · CEFR C1 · Informal

very silly, dangerous, or not sensible.

For teachers: extremely foolish, eccentric, or irrational. Often used to describe ideas, policies, or behaviors that seem to lack any logic.

- It was a lunatic idea to go hiking in the middle of a storm.
- The critics dismissed the proposal as a lunatic fringe theory that lacked any empirical evidence or logical foundation.

Usage: Commonly appears in the fixed expression 'lunatic fringe' to describe extreme or radical groups.

### 3. related to the moon

adjective · CEFR C2 · Archaic · Literary

having to do with the moon.

For teachers: relating to or influenced by the moon. This sense is the word's original etymological root but is now rarely encountered outside of historical or poetic contexts.

- The old book discussed the lunatic cycles and their effect on the tides.
- In the poet's vision, the lunatic light of the full moon transformed the familiar landscape into something alien and cold.

Usage: Almost entirely replaced by 'lunar' in modern scientific and general contexts.

Teaching tip: Learners will likely only see this in 19th-century literature or older texts.

## Examples

- He drives like a lunatic on the highway.
- The neighbors thought he was a lunatic for trying to build a giant boat in his tiny backyard.

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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.