[ sluhj ]
See synonyms for sludge on
  1. mud, mire, or ooze; slush.

  2. a deposit of ooze at the bottom of a body of water.

  1. any of various more or less mudlike deposits or mixtures.

  2. the sediment in a steam boiler or water tank.

  3. broken ice, as on the sea.

  4. a mixture of some finely powdered substance and water.

  5. sediment deposited during the treatment of sewage.

  6. Also called activated sludge. Bacteriology. sewage sediment that contains a heavy growth of microorganisms, resulting from vigorous aeration.

  7. a fine, mudlike powder produced by a mining drill.

Origin of sludge

First recorded in 1640–50; variant of dialectal slutch, slitch,Middle English slich “slime, wet mud” (compare its derivative slucched “muddy”); apparently of expressive origin

Other words from sludge

  • de-sludge, verb (used with object), de-sludged, de-sludg·ing.

Words Nearby sludge Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use sludge in a sentence

British Dictionary definitions for sludge


/ (slʌdʒ) /

  1. soft mud, snow, etc

  2. any deposit or sediment

  1. a surface layer of ice that has a slushy appearance

  2. (in sewage disposal) the solid constituents of sewage that precipitate during treatment and are removed for subsequent purification

Origin of sludge

C17: probably related to slush

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012