\ˈsləj \

Definition of sludge 

1 : mud, mire especially : a muddy deposit (as on a riverbed) : ooze

2 : a muddy or slushy mass, deposit, or sediment: such as

a : precipitated solid matter produced by water and sewage treatment processes

b : muddy sediment in a steam boiler

c : a precipitate or settling (such as a mixture of impurities and acid) from a mineral oil

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Other Words from sludge

sludgy \ˈslə-jē \ adjective

Synonyms for sludge


guck (or gook), mire, muck, mud, ooze, slime, slop, slush

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Examples of sludge in a Sentence

after a day of heavy rain, the fairgrounds had turned into pure sludge I can't bring myself to read that sludge.

Recent Examples on the Web

Hall was not always opposed to the sludge operation using the rail yard in Parrish. Dennis Pillion,, "Sewage sludge train cars in Birmingham to be moved after 'death smell' complaints," 6 Mar. 2018 Harrington is an expert who got the idea after being called in to help clean up after the Gold King Mine blowout in southern Colorado, which unleashed toxic sludge into waterways. Alicia Acuna, Fox News, "Colorado town hopes to strike gold by converting abandoned mine into fresh water reservoir," 3 July 2018 Pictures taken in 1992 show standing pools of black sludge where two underground storage tanks were removed. Brian Slodysko, Houston Chronicle, "Pence family gas stations left costly environmental legacy," 13 July 2018 Pictures taken in 1992 show standing pools of black sludge where two underground storage tanks were removed. Brian Slodysko,, "Cleanup of Pence family gas stations cost Indiana more than $20 million," 13 July 2018 Fallen trees and sludge are blocking tunnels on the main highways, slowing the flow of goods in mountainous Japan. Mayumi Negishi, WSJ, "Japan Flooding, Mudslides Kill More Than a Hundred People," 9 July 2018 Sometimes Colombo will unearth old coins, bottles or jewelry in the sand and sludge. Lizzie Johnson, San Francisco Chronicle, "Stinson Beach parking lot still crumbling after storm — and fix is uncertain," 10 Apr. 2018 The sludge is a byproduct of New Yorkers’ excrement. Washington Post, "Alabama mayor: ‘Poop train’ finally empty; sludge gone," 19 Apr. 2018 The landfill in Adamsville got approval in December 2016 from the Alabama Department of Environmental Management to import the sludge from seven wastewater treatment plants in New York and New Jersey to use as alternative cover for the landfill. Dennis Pillion,, "New York poop train won't derail Parrish Coal Fest," 6 Apr. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'sludge.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of sludge

15th century, in the meaning defined at sense 1

History and Etymology for sludge

Middle English slugge, perhaps alteration of slicche mud, slush; akin to Old High German slīh mire

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Dictionary Entries near sludge


slub yarn



sludge acid



Statistics for sludge

Last Updated

16 Sep 2018

Look-up Popularity

Time Traveler for sludge

The first known use of sludge was in the 15th century

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More Definitions for sludge



English Language Learners Definition of sludge

: thick, soft, wet mud

: a soft, thick material that is produced in various industrial processes (such as in the treatment of sewage)

: a thick material that can form in the oil in an engine and cause engine problems


\ˈsləj \

Kids Definition of sludge

: a soft muddy mass resulting from sewage treatment


\ˈsləj \

Medical Definition of sludge 

(Entry 1 of 2)

: a semisolid precipitated mass or deposit biliary sludge especially : sludged blood

sludged; sludging

Medical Definition of sludge (Entry 2 of 2)

: to form sludge positions that cause blood to sludge— L. K. Altman

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Comments on sludge

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