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

Many traditional litters either clump too softly or clump while gradually turning into dusty sludge that sticks and smells over time. —Svetlana Khachiyan, USA Today, 19 Dec. 2025

The sludge and water spewing forth mirrors the instability of her psychic state. —Angelica Jade Bastién, Vulture, 19 Dec. 2025

As the biofilm degrades, sludge settles in a secondary clarifier. —Aamir Khollam, Interesting Engineering, 18 Dec. 2025

During World War II and throughout the Cold War, the Hanford reactors along the Columbia River near Richland, Washington produced most of the plutonium in the US arsenal of bombs and missiles, leaving behind 56 million gallons of radioactive sludge stored in 177 aging underground tanks. —New Atlas, 14 Dec. 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