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 of sludge

• 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

The Dish Rack and Drip Tray The drying rack does an important job, but the tray underneath often becomes a breeding ground for mold and sludge. —Jessica Safavimehr, Southern Living, 27 Feb. 2026

Since the notice, a spokesman said the city has cleared two sedimentation bins of sludge and expects to have all the sludge cleared by April 10. —Briah Lumpkins, Charlotte Observer, 25 Feb. 2026

Sewage sludge is a mud-like byproduct created during wastewater treatment. —Peter Blair, Baltimore Sun, 21 Feb. 2026

Those policies range from outright bans to water standards, sludge spreading restrictions and cleanup funding. —Jennifer Bringle, Sourcing Journal, 19 Feb. 2026

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