/ Dictionary / Index M methylene group: Meaning and Definition of Find definitions for: meth'ylene group" Pronunciation: [key] the bivalent organic group >CH, derived from methane. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. methylene dioxyamphetamine methylene iodide Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language