Definition of sludge
2
: a muddy or slushy mass, deposit, or sediment: such as
a
: precipitated solid matter produced by water and sewage treatment processes
b
: muddy sediment in a steam boiler
c
: a precipitate or settling (such as a mixture of impurities and acid) from a mineral oil
3
: slush sense 5
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Merriam-Webster unabridged
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Time Traveler for sludge
The first known use of sludge was in the 15th century
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