Synonyms/Hypernyms (Ordered by Estimated Frequency) of noun sludge

2 senses of sludge

Sense 1
sludge -- (the precipitate produced by sewage treatment)
       => precipitate -- (a precipitated solid substance in suspension or after settling or filtering)

Sense 2
sludge, slime, goo, goop, gook, guck, gunk, muck, ooze -- (any thick, viscous matter)
       => matter -- (that which has mass and occupies space; "physicists study both the nature of matter and the forces which govern it")