/ Thesaurus / S Synonyms of slack water Find synonyms for: Noun1. slack, slack water, stretchusage: a stretch of water without current or movement; "suddenly they were in a slack and the water was motionless"2. slack water, slack tide, tideusage: the occurrence of relatively still water at the turn of the (low) tideWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: languid Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language