/ Dictionary / Index E ethynyl group: Meaning and Definition of Find definitions for: ethy'nyl group" Pronunciation: [key] — Chem. Chem. the univalent group HC=C−, derived from acetylene. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ethynylation ETI Related Content Daily Word Quiz: hedonist Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language