/ Thesaurus / S Synonyms of septic tank Find synonyms for: Noun1. septic tank, tank, storage tankusage: large tank where solid matter or sewage is disintegrated by bacteriaWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: kiln Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language