/ Thesaurus / C Synonyms of carbon monoxide gas Find synonyms for: Noun1. carbon monoxide, carbon monoxide gas, CO, monoxideusage: an odorless very poisonous gas that is a product of incomplete combustion of carbonWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: reticent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language