Meaning of embryonic disk

em'bryon'ic disk'

Pronunciation: [key]
— Embryol. Embryol.
  1. Also calledin the early embryo of mammals, the flattened inner cell mass that arises at the end of the blastocyst stage and from which the embryo begins to differentiate.
  2. the blastodisk of yolky eggs.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.