/ Thesaurus / U Synonyms of unsoundable Find synonyms for: Adjective1. unsoundable, unfathomable (vs. fathomable)usage: too deep to determine the depth ofWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: acquiesce Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language