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

Dancing with an old fave will be almost as exciting as getting a glimpse of the primordial riverbed, which is usually covered with sludge. —Brittany Allen, Literary Hub, 13 Mar. 2026

Little filth flies such as drain flies breed in sludge and decaying matter that can build up in drain pipes, says Oi. —Arricca Elin Sansone, Southern Living, 4 Mar. 2026

In response, Synagro started shedding some of its liquid sludge contracts, said Steve D'Agostino, Woonsocket's public works director. —Alex Kuffner, The Providence Journal, 3 Mar. 2026

Ask what went into bagged or bulk compost, and favor products made from yard waste, leaves, or clean food scraps over those blended with municipal solid waste or sewage sludge. —Dr. Avishesh Neupane, Hartford Courant, 7 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