/ Dictionary / Index M methylidyne group: Meaning and Definition of Find definitions for: me•thyl'i•dyne group" Pronunciation: (me-thil'i-dīn"), [key] — Chem. Chem. the trivalent group ≡CH. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. methylic methylisobutenyl ketone Related Content Daily Word Quiz: supine Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language