/ Thesaurus / M Synonyms of metaphosphoric acid Find synonyms for: Noun1. metaphosphoric acid, polyphosphoric acidusage: a glassy solid acid ([HPO3]n) often used as a dehydrating agentWordNet 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