# slag

/ˈsɫæɡ/ (US) · /slˈæɡ/ (UK)

Source: https://englishreference.com/word/slag
Updated: 2026-08-27

## Senses

### 1. industrial waste

noun · CEFR C1 · Technical

the waste material that is left over after metal has been removed from rock.

For teachers: the stony waste matter separated from metals during the smelting or refining of ore.

- The old factory was surrounded by huge piles of black slag left over from the steel production.
- Road builders often use crushed slag as a base material because of its durability and the way it compacts under heavy loads.

Usage: Uncountable when referring to the material generally; countable when referring to specific types or deposits.

### 2. insult for a person

noun · CEFR C2 · British English · Slang · Vulgar

a very rude and offensive word for someone, usually a woman, who is thought to have many sexual partners.

For teachers: a highly derogatory and vulgar term for a person perceived as promiscuous; occasionally used as a general term of contempt.

- He got into a fight after calling the girl a slag in front of her friends.
- The tabloid was criticised for using gendered insults like 'slag' to describe the actress's private life.

Teaching tip: This is a severe insult in British English. It is almost exclusively used in the UK and Ireland and is considered highly offensive and sexist.

### 3. to criticise someone

verb · CEFR C1 · British English · Informal

to say unkind or critical things about someone, especially when they are not there.

For teachers: to criticise or malign someone in a harsh or mocking way; frequently appears in the phrasal form 'slag off'.

- It is not fair to slag him off just because he made one mistake.
- The two comedians spent the entire podcast slagging off their former agent for his lack of professional ethics.

Usage: Usually transitive, requiring an object. In British English, 'slag off' is the most common idiomatic form.

## Examples

- He was being very rude and called her a slag.
- The tabloid was criticized for using words like slag to describe young women in the public eye.

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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.