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
Next to the sculpture are barrels of toxic "slag" leftover from the melting process.
From BBC ● Oct. 19, 2025
“There were high concentrations of slag in these, which is a glass-like material that makes them maybe a little bit more brittle in the cold,” she says.
From BBC ● Aug. 13, 2024
"And if you get the balance right and cool the slag quickly enough, you end up with reactivated cement, without adding any cost to the steelmaking process."
From Science Daily ● May 22, 2024
“All impurities burned out and ready for a glorious flux, and for that—more fire. And then either the slag heap or, perhaps what no one in the world ever quite gives up, perfection.”
From "East of Eden" by John Steinbeck
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
"Anyone that we haven't slagged off," jokes Mica.
From BBC ● May 8, 2022
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
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
Sam was now slagging one of his original investors, who then became his biggest competitor.
From Slate ● Oct. 5, 2023
He said: "No, we read Vanity Fair - they're slagging each other off in the pages... You don't need to go for lunch with those people."
From BBC ● May 26, 2023
“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
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
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
