From Longman Dictionary of Contemporary Englishsludgesludge /slʌdʒ/ noun [uncountable] 1 DNsoft thick mud, especially at the bottom of a liquid2 TIRUBBISH/WASTEthe solid substance that is left when industrial waste or sewage (=the liquid waste from toilets) has been cleaned3 TTCRUBBISH/WASTEthick dirty oil in an engine —sludgy adjective
Examples from the Corpus
sludge• H., once handed out bricks of dried sludge to City Council members at a budget meeting.• Incinerating sludge costs £9 a tonne and land disposal £3 a tonne.• A considerable amount of sludge comes from lime-soda-softening, the amount increasing with the hardness of the water.• For instance, he interfered with the hauling of sludge, causing sludge to back up at the plant, they said.• The resultant sludge is washed with twice its weight of water and then filtered.• Fully-digested sewage sludge is also used, with considerable success.• Sewage sludge and industrial waste will still enter the North Sea from Britain until 1998.• The sludge in the Cuisinart fills the condo with smells I remember from nature trails of my childhood.Origin sludge (1600-1700) Probably from slush 