goo vs sludge

goo and sludge both are nouns.

Word	Noun	Adjective	Verb	Adverb
goo	Yes	No	No	No
sludge	Yes	No	No	No

As nouns, goo and sludge are synonyms defined as:

Other synonyms of goo include gook, goop, guck, gunk, muck, ooze, slime.

goo (noun)	sludge (noun)
any thick, viscous matter	any thick, viscous matter
	the precipitate produced by sewage treatment