slag
1 Americannoun
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Also called cinder. the more or less completely fused and vitrified matter separated during the reduction of a metal from its ore.
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the scoria from a volcano.
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waste left over after the re-sorting of coal.
verb (used with object)
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to convert into slag.
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Metallurgy. to remove slag from (a steel bath).
verb (used without object)
noun
noun
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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
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a mass of rough fragments of pyroclastic rock and cinders derived from a volcanic eruption; scoria
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a mixture of shale, clay, coal dust, and other mineral waste produced during coal mining
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slang a coarse or dissipated girl or woman
verb
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slang (tr) (usually foll by off) to abuse (someone) verbally
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slang (intr) to spit
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
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
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
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
Excavations and geophysical surveys in this area revealed crucibles, slag, and tin bronze artifacts.
From Science Daily ● Dec. 5, 2025
She argues that incineration increases residual slag and releases harmful toxins like mercury and dioxins.
From BBC ● Jan. 22, 2025
"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
I have been waiting for it ever since Smithy and Mara became felters overnight, even though they still carried the slag metal everywhere.
From "The Many Assassinations of Samir, the Seller of Dreams" by Daniel Nayeri
Lieberstein previously worked on "The Office" as one of its producers and as Toby, the bland HR representative everyone slagged off on.
From Salon ● Mar. 19, 2023
Executives who didn’t take her calls risked being slagged on Deadline.
From New York Times ● Jan. 21, 2023
Anyway, you’ll be happy to hear, I fought through my misgivings and slagged the performance—but it struck me that if I was thinking about these questions in this context, these questions have permeated very deep.
From Slate ● Dec. 19, 2018
Bono got slagged off for trying to give Liam the “Bono chat”, where he explains the mysteries of rock stardom to young up-and-comers: “Wish I’d had an out-of-body experience instead. Not in my Top 50.”
From The Guardian ● Aug. 10, 2017
Hardly big enough so a cat could slip through, and under it is this big pile of coal slagged up against the foundation wall.
From "Freak The Mighty" by Rodman Philbrick
Greater Manchester Mayor Andy Burnham has denied "slagging off" London when calling for better treatment for his own region from the government.
From BBC ● Sep. 28, 2021
“This is not about slagging anyone off in this TV series at all,” he said.
From Seattle Times ● Jul. 16, 2021
Fearn doesn’t share the inclination, saying, “I’ve never really been into slagging bands off. It’s just not my thing.”
From Washington Post ● Jan. 21, 2021
YouTube videos were dedicated to slagging her off.
From The Guardian ● Nov. 16, 2020
Gary Drake and Ross Wilcox might’ve been slagging me off, but the fainter the voices became, the less I wanted to go back.
From "Black Swan Green" by David Mitchell
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Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
