/ Dictionary / Index M metasomatism: Meaning and Definition of Find definitions for: met•a•so•ma•tism Pronunciation: (met"u-sō'mu-tiz"um), [key] — n. Geol. the series of metamorphic processes whereby chemical changes occur in minerals or rocks as a result of the introduction of material, often in hot aqueous solutions, from external sources. replacement (def. 4). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. metasequoia metastable Related Content Daily Word Quiz: diligent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language