slag

¹ American  

[slag] / slæg /

noun

1. Also called cinder.  the more or less completely fused and vitrified matter separated during the reduction of a metal from its ore.

2. the scoria from a volcano.

3. waste left over after the re-sorting of coal.

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verb (used with object)

slagged, slagging

1. to convert into slag.

2. Metallurgy. to remove slag from (a steel bath).

verb (used without object)

slagged, slagging

1. to form slag; become a slaglike mass.

slag ² American  

[slag] / slæg /

noun

1. British Slang. an abusive woman.

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slag British  

/ slæɡ /

noun

1. Also called: cinder.  the fused material formed during the smelting or refining of metals by combining the flux with gangue, impurities in the metal, etc. It usually consists of a mixture of silicates with calcium, phosphorus, sulphur, etc See also basic slag

2. a mass of rough fragments of pyroclastic rock and cinders derived from a volcanic eruption; scoria

3. a mixture of shale, clay, coal dust, and other mineral waste produced during coal mining

4. slang a coarse or dissipated girl or woman

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verb

1. slang (tr) (usually foll by off) to abuse (someone) verbally

2. slang (intr) to spit

slag Scientific  

/ slăg /

1. The vitreous mass left as a residue by the smelting of metallic ore. It consists mostly of the siliceous and aluminous impurities from the iron ore.

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Usage

What else does slag mean? Content warning: the following content includes references to strong and sexist language. In slang, slag is an insulting British English term for a contemptible person. When used of women, it can be equivalent to slut. As a verb, to slag (off somebody) is "to attack (them) verbally," i.e., to talk smack about them.

Other Word Forms

• slagability
  noun
• slagging
  noun
• slaglessness
  noun
• slagable
  adjective
• slaggy
  adjective
• slagless
  adjective
• unslagged
  adjective

Etymology

Origin of slag¹

1545–55; < Middle Low German slagge; cognate with German Schlacke dross, slag; see slack ²

Origin of slag²

First recorded in 1780–90; originally an argot word for a worthless person or a thug; perhaps identical with slag ¹

Example Sentences

Former Ulster wing Trimble said: "They are so bad we actually feel sorry for them, we don't even slag them. Let's do them a favour and slag them."

From BBC • Mar. 6, 2026

Copper, steel, aluminum and precious metals can be recovered, but rare-earth metals typically fuse with other byproducts in waste called slag.

From The Wall Street Journal • Jan. 23, 2026

He has spent time exploring and photographing the area's trails and hillsides dotted with slag heaps of slate spoils, its old quarry sites and abandoned machinery.

From BBC • Dec. 28, 2024

"We found the combination of cement clinker and iron oxide is an excellent steelmaking slag because it foams and it flows well," said Dunant.

From Science Daily • May 22, 2024

Smithy and Mara were busy sorting the metal slag that they would have to leave behind and the tools they could pack onto the camels.

From "The Many Assassinations of Samir, the Seller of Dreams" by Daniel Nayeri

Related Words

• lava