/ Dictionary / Index M mesoderm: Meaning and Definition of Find definitions for: mes•o•derm Pronunciation: (mez'u-dûrm", mes'-, mē'zu-, -su-), [key] — n. Embryol. the middle germ layer of a metazoan embryo. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: mesoderm (Thesaurus) mesocyclone mesodont Related Content Daily Word Quiz: abstain Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language