/ Thesaurus / N Synonyms of nitrogen dioxide Find synonyms for: Noun1. nitrogen dioxide, dioxide, gasusage: a highly poisonous brown gas (NO2)WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: reclusive Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language