/ Dictionary / Index M mastocarcinoma: Meaning and Definition of Find definitions for: mas•to•car•ci•no•ma Pronunciation: (mas"tō-kär"su-nō'mu), [key] — pl. -mas, -ma•ta carcinoma of the breast. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. masto- mastocytosis Related Content Daily Word Quiz: censure Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language