[ slag ]
/ slæg /
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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.
the scoria from a volcano.
waste left over after the re-sorting of coal.
verb (used with object), slagged, slag·ging.
to convert into slag.
Metallurgy. to remove slag from (a steel bath).
verb (used without object), slagged, slag·ging.
to form slag; become a slaglike mass.
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Origin of slag

1545–55; <Middle Low German slagge; cognate with German Schlacke dross, slag; see slack2


Other definitions for slag (2 of 2)

[ slag ]
/ slæg /

British Slang. an abusive woman.

Origin of slag

First recorded in 1780–90; originally an argot word for a worthless person or a thug; perhaps identical with slag1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023


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.

Where does slag come from?

Outside of slang, slag refers to residue from the process of smelting, a method used to separate a metal from raw ore. This slag comes from a German root and has been recorded in English since the 1550s.

The British slang slag, for a “worthless or objectionable person,” is seen by the late 1700s. Its origin is unclear, but the smelting slag may have contributed a sense of “useless detritus.”

From this sense of “contemptible person,” slag expanded to all types of people or things considered unsavory. In the early 1900s, according to Green’s Dictionary of Slang, we can find slag for a “rough person,” “nonsense,” and “petty criminal,”

One particular extension of slag is slang for “prostitute” or “promiscuous woman,” equivalent to slut or whore. This sense emerges by the mid-1900s, and is considered offensive and sexist.

Another use of slag is as a verb, usually in the verb phrase slag off. This means “to verbally abuse (someone),” e.g., He was slagging me off by calling me an idiot. This use has been recorded as early as the 1960s.

The English rock band the Arctic Monkeys notably used slag in their 2007 song “Fluorescent Adolescent”: “Oh, the boy’s a slag, the best you ever had.” Here, slag is apparently characterizing a male as being sexually promiscuous.

How is slag used in real life?

While not as coarse as some slurs or swears, slag is considered offensive. When used of women, it’s even more insulting and can be considered sexist.

Slagging (someone off) isn’t a nice thing to do, but using the slang verb isn’t as offensive as outright calling someone a slag.

More examples of slag:

“To get slagged off by Noel [Gallagher] was, for me, a real life-affirming moment,” says [Lewis] Capaldi. Would he like to slag off anyone in return? ‘That’s not really my move. Ask me at the end of the year.’”
—Elle Hunt, Guardian, June 2019


This content is not meant to be a formal definition of this term. Rather, it is an informal summary that seeks to provide supplemental information and context important to know or keep in mind about the term’s history, meaning, and usage.

How to use slag in a sentence

British Dictionary definitions for slag

/ (slæɡ) /

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, etcSee also basic slag
a mass of rough fragments of pyroclastic rock and cinders derived from a volcanic eruption; scoria
a mixture of shale, clay, coal dust, and other mineral waste produced during coal mining
British slang a coarse or dissipated girl or woman
verb slags, slagging or slagged
(tr) British slang (usually foll by off) to abuse (someone) verbally
(intr) Australian slang to spit

Derived forms of slag

slagging, nounslaggy, adjective

Word Origin for slag

C16: from Middle Low German slagge, perhaps from slagen to slay
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for slag

[ slăg ]

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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.