/ Dictionary / Index M megaspore: Meaning and Definition of Find definitions for: meg•a•spore Pronunciation: (meg'u-spôr", -spōr"), [key] — n. Bot. the larger of the two kinds of spores characteristically produced by seed plants and a few fern allies, developing into a female gametophyte. Cf. the embryo sac of a flowering plant. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: megaspore (Thesaurus) megasporangium megasporophyll 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