Synonyms for sludge Found 8 synonyms across 1 meaning for “sludge”. any thick, viscous matter (noun) slimegoogoopgookguckgunkmuckooze Explore Related Words Rhymes with sludgeSynonyms for slimeSynonyms for gooSynonyms for goopSynonyms for gookSynonyms for guck Synonym Finder | Rhyme Finder | Poetry Editor