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

Related Stories The report noted that sludge remained Saitex’s primary source of waste in 2025, and that the company repurposed 40 percent of that waste to produce bricks for garden walkways and concrete blocks for retaining walls. — Jennifer Bringle, Footwear News, 21 Aug. 2026

Currently, the Louisiana sludge metal band has been busy headlining arenas across North America and opening stadiums in the UK and Europe for the likes of System of a Down and Queens Of The Stone Age. — Quentin Thane Singer, Forbes.com, 17 Aug. 2026

The ball rolled to the sticky floor, littered with crushed six-pack carriers and a fine layer of winter sludge, and two competitors dove to fetch it. — Literary Hub, 11 Aug. 2026

Rather than paying millions to haul away toxic sludge, facilities could soon scrub their rinse water for immediate reuse to harvest high-purity copper directly off their treatment equipment. — Mrigakshi Dixit, Interesting Engineering, 3 Aug. 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