from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A flattened, disklike region of cells from which the embryo begins to develop in the fertilized ovum of many vertebrate species. Also called blastodisk, embryonic disk.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. a small circular white spot on the surface of the yolk of an egg
Sorry, no etymologies found.