/ Dictionary / Index M monophthong: Meaning and Definition of Find definitions for: mon•oph•thong Pronunciation: (mon'uf-thông", -thong"), [key] — n. Phonet. a vowel retaining the same quality throughout its duration. Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. monophosphate monophthongize Related Content Daily Word Quiz: winsome Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language