/ Dictionary / Index M molecular orbital: Meaning and Definition of Find definitions for: molec'ular or'bital Pronunciation: [key] See under(def. 2a). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. molecular knife molecular sieve Related Content Daily Word Quiz: kiln Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language