Meaning of SLUDGE in English

SLUDGE

sludge /slʌdʒ/ BrE AmE noun [uncountable]

[ Date: 1600-1700 ; Origin: Probably from slush ]

1 . soft thick mud, especially at the bottom of a liquid

2 . the solid substance that is left when industrial waste or ↑ sewage (=the liquid waste from toilets) has been cleaned

3 . thick dirty oil in an engine

—sludgy adjective

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.