/ Dictionary / Index M mesocardium: Meaning and Definition of Find definitions for: mes•o•car•di•um Pronunciation: (mez"u-kär'dē-um, mes"-, mē"zu-, -su-), [key] — pl. -di•a the double layer of splanchnic mesoderm supporting the embryonic heart. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. mesoblast mesocarp Related Content Daily Word Quiz: philtrum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language