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

In a victory for environmental groups, Calhoun settled the case in 2024 and agreed to filter its water for PFAS, stop spreading sludge, test private drinking wells and keep the community informed of risk. —Dylan Jackson, ABC News, 6 May 2026

Start by pouring a pot of boiling water into the drain to loosen any sludge and kill the gnats. —Karen Brewer Grossman, Southern Living, 5 May 2026

When the basin’s draining began in late March, some in the community worried about turtles being left behind in the sludge. —Victoria Le, Oc Register, 24 Apr. 2026

Interestingly, the local sewage sludge was pretreated, resulting in a 200 percent increase in renewable natural gas production while cutting disposal costs in half. —Mrigakshi Dixit, Interesting Engineering, 22 Apr. 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