See more synonyms for sludge on
  1. mud, mire, or ooze; slush.
  2. a deposit of ooze at the bottom of a body of water.
  3. any of various more or less mudlike deposits or mixtures.
  4. the sediment in a steam boiler or water tank.
  5. broken ice, as on the sea.
  6. a mixture of some finely powdered substance and water.
  7. sediment deposited during the treatment of sewage.
  8. Also called activated sludge. Bacteriology. sewage sediment that contains a heavy growth of microorganisms, resulting from vigorous aeration.
  9. a fine, mudlike powder produced by a mining drill.

Origin of sludge

1640–50; variant of dial. slutch, slitch, Middle English slich slime, wet mud (compare its derivative slucched muddy); apparently of expressive orig.
Related formsde-sludge, verb (used with object), de-sludged, de-sludg·ing. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for sludge

goo, grease, silt, slime, muck, sediment, gunk, oil, slop, mire, ooze, scum, glop, goop

Examples from the Web for sludge

Contemporary Examples of sludge

Historical Examples of sludge

British Dictionary definitions for sludge


  1. soft mud, snow, etc
  2. any deposit or sediment
  3. a surface layer of ice that has a slushy appearance
  4. (in sewage disposal) the solid constituents of sewage that precipitate during treatment and are removed for subsequent purification

Word Origin for 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

Word Origin and History for sludge

"mud, mire, ooze," 1640s, of uncertain origin, possibly a variant of Middle English slutch "mud, mire," or a variant of slush (n.).

Online Etymology Dictionary, © 2010 Douglas Harper