/ Dictionary / Index M montmorillonite: Meaning and Definition of Find definitions for: mont•mo•ril•lon•ite Pronunciation: (mont"mu-ril'u-nīt"), [key] — n. any of a group of clay minerals characterized by the ability to expand when they absorb large quantities of water. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Montmorency Montparnasse Related Content Daily Word Quiz: clairvoyant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language