sludge

noun

ˈsləj 

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

3

: slush sense 5

sludgy

ˈslə-jē 

adjective

Synonyms

• mud

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

Using more sludge and less slag in their recipe, researchers were able to create a material that's stronger than even today's enhanced cements and highly resistant to corrosion by acid. —Michael Franco, New Atlas, 9 June 2025

The film careens between a dreary sludge of despair and eventual heart-palpitating nightmare, Grace caught in a mercurial storm of her own moods without ballast and unable to be understood by those around her. —Ryan Lattanzio, IndieWire, 17 May 2025

The blasting flames start to slowly heat a giant vat holding hundreds of gallons of goopy, waxy sludge above. —Kat Lonsdorf, NPR, 1 Apr. 2025

What To Do: Use a stiff drain brush and enzymatic drain cleaner to clear out sludge. —Arricca Elin Sansone, Southern Living, 16 Mar. 2025

Word History

Etymology

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

Rhymes for sludge

• budge
• drudge
• frage
• fudge
• grudge
• judge
• mudge
• nudge
• rudge
• smudge
• trudge
• adjudge

Kids Definition

sludge

noun

ˈsləj 

1

: mud, mire

2

: a muddy or slushy mass

especially : solid matter produced by water and sewage treatment processes

sludgy

ˈsləj-ē 

adjective

Medical Definition

sludge

1 of 2 noun

ˈsləj 

: a semisolid precipitated mass or deposit

biliary sludge

especially : sludged blood

sludge

2 of 2 intransitive verb

sludged; sludging

: to form sludge

positions that cause blood to sludge

—L. K. Altman