/ Dictionary / Index M mastocytosis: Meaning and Definition of Find definitions for: mas•to•cy•to•sis Pronunciation: (mas"tō-sī-tō'sis), [key] — n. Pathol. an overproduction of mast cells in body tissues. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. mastocarcinoma mastodon Related Content Daily Word Quiz: panacea Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language