/ Dictionary / Index E ectoblast: Meaning and Definition of Find definitions for: ec•to•blast Pronunciation: (ek'tu-blast"), [key] — n. Embryol. the ectoderm. epiblast. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: ectoblast (Thesaurus) ecto- ectocommensal Related Content Daily Word Quiz: deleterious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language