: mud, mire
especially : a muddy deposit (as on a riverbed) : ooze
: a muddy or slushy mass, deposit, or sediment: such as
: precipitated solid matter produced by water and sewage treatment processes
: muddy sediment in a steam boiler
: a precipitate or settling (such as a mixture of impurities and acid) from a mineral oil
sludgy adjective

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 Filling in Babyn Yar had a larger purpose than disposing of excess sludge. Joshua Hammer, Smithsonian Magazine, 29 Nov. 2023 The search for survivors was hampered by damaged roads, poor communications and bad weather, and residents were struggling to clear sludge and debris in the wake of one of the worst disasters in the remote region in more than 50 years. Reuters, CNN, 9 Oct. 2023 Imagining a future university student would figure out how to add a binder or resin to that plastic, and that a contractor would try to add a little color, O’Toole came up with the idea for a gray-pink plastic sludge, which could then be molded or 3D printed. Abbey White, The Hollywood Reporter, 28 Oct. 2023 Meanwhile, rats scurry by and some mysterious black sludge oozes out of the walls—maybe from the same holes that floodwaters shot out of today. Kate Aronoff, The New Republic, 29 Sep. 2023 Among those who trekked through the sludge was DJ Diplo, who spent hours hiking in the mud to try to get to his concert hours later in Washington, DC. Nouran Salahieh, CNN, 4 Sep. 2023 Here’s how to get one Feb. 9, 2023 Later, at processing facilities around the city, the bags will be stripped off and any foreign objects removed from the sludge. Max Kim, Los Angeles Times, 24 Aug. 2023 The process is energy intensive — often fueled by greenhouse-gas-emitting fossil fuels — and produces a thick, briny sludge on the back-end that is typically released back into the ocean. Hayley Smith, Los Angeles Times, 19 Sep. 2023 In China’s Lake Taihu, the blooms are so bad that authorities have battled for years to physically remove the sludge with special machines that chew it up using hundreds of tiny teeth. Chris Baraniuk, WIRED, 11 Sep. 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'sludge.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


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

First Known Use

15th century, in the meaning defined at sense 1

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

Dictionary Entries Near sludge

Cite this Entry

“Sludge.” Dictionary, Merriam-Webster, Accessed 11 Dec. 2023.

Kids Definition


: mud, mire
: a muddy or slushy mass
especially : solid matter produced by water and sewage treatment processes
sludgy adjective

Medical Definition


1 of 2 noun
: a semisolid precipitated mass or deposit
biliary sludge
especially : sludged blood


2 of 2 intransitive verb
sludged; sludging
: to form sludge
positions that cause blood to sludgeL. K. Altman

More from Merriam-Webster on sludge

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