/ Thesaurus / U Synonyms of unattackable Find synonyms for: Adjective1. impregnable, inviolable, secure, strong, unassailable, unattackable, invulnerable (vs. vulnerable)usage: immune to attack; incapable of being tampered with; "an impregnable fortress"; "fortifications that made the frontier inviolable"; "a secure telephone connection"WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language