/ Dictionary / Index S synthesis gas: Meaning and Definition of Find definitions for: syn'thesis gas" Pronunciation: [key] — Chem. Chem. any of several gaseous mixtures consisting essentially of carbon monoxide and hydrogen, used in the synthesis of chemical compounds, as ammonia and alcohols. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. synthesis synthesize Related Content Daily Word Quiz: supercilious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language