\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

The bottoms of the ponds are layered with solid pig waste that naturally sinks to form a sludge. Ben Kesling, WSJ, "Florence Flooding Hits North Carolina Hog Farms Hard," 19 Sep. 2018 Biosolids are left over at a treatment plant after bacteria decomposes human waste into sludge fertile with nitrogen and phosphorus compounds. Kevin Spear,, "Rare Florida jewel, Blue Cypress Lake, sickens with pollution," 11 Apr. 2018 Within a month gasoline starts to separate, and after a year or two evaporates into a caramel-like sludge that coats the inside of your fuel tank. Matt Jancer, Popular Mechanics, "How To Resurrect a Sleeping Car," 7 Feb. 2018 Hearing scheduled today There are multiple legal challenges to the sludge importation currently in the court system. Dennis Pillion,, "Sludge fight: Legal battles over imported sewage waste rage on in Jefferson County," 19 Jan. 2018 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

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

9 Dec 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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More from Merriam-Webster on sludge

Rhyming Dictionary: Words that rhyme with sludge

Thesaurus: All synonyms and antonyms for sludge

Spanish Central: Translation of sludge

Nglish: Translation of sludge for Spanish Speakers

Britannica English: Translation of sludge for Arabic Speakers

Comments on sludge

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having a pattern of small flowers

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