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

British Dictionary definitions for desludging


  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 desludging



"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