What does sludge mean?
Sludge is a noun for a thick, muddy, oily, or slimy mass of material, such as waste, sediment, or sewage. It can also describe writing, speech, or broadcasting that is considered dull, muddled, unpleasant, or of poor quality. The literal word is especially common in environmental, industrial, and wastewater contexts, where it refers to material that is both messy and potentially hazardous. Figuratively, “political sludge” conveys the idea of confused rhetoric or tedious, uninspiring communication. Sludge is usually treated as an uncountable mass noun rather than as a countable object, although the verb “to sludge” exists in the sense of moving slowly or heavily through mud or sludge.
A thick, muddy, slimy, or oily mass of material, especially sediment or waste.
"The drain was blocked by sludge and old leaves."
Often uncountable; used particularly for sewage, industrial waste, and oily sediment.
To move slowly or heavily through mud, sludge, or a similar thick substance.
"The old truck sludged across the muddy track."
Relatively uncommon and chiefly descriptive.
Usually uncountable when referring to mud, waste, or sediment; the plural is more likely when referring to separate masses or deposits.
"Several sludges had collected beneath the damaged pipes."
From sewage to politics, sludge is what remains when something useful settles into something slow, thick, and difficult to handle.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does sludge come from?
The word sludge is of uncertain origin and its early history is not fully clear. It appears in English during the medieval period in the sense of mud or slime, and its modern figurative meanings developed later by analogy with material that is thick, obstructive, and unpleasant. Because the precise source and related cognates are uncertain, no firm etymological relationship should be inferred beyond its established English development.
Related word forms
How sludge is actually used
In its literal sense, sludge commonly describes thick mud, sewage, industrial waste, or oily sediment. The figurative sense is informal and usually disparaging, especially in political and cultural criticism.
Easily confused with sludge
Sludge is a thick mass of mud, waste, or sediment, whereas slush is usually loose, watery snow or a wet mixture of snow and water.