Pronunciation: (kôr"ē-ō-u-lan'tō-is, -tois, kōr"-), [key]
—n. Embryol., Zool.
a vascular, extraembryonic membrane of birds, reptiles, and certain mammals, formed by the fusion of the wall of the chorion with the wall of the allantois. Also called cho'rioallanto'ic mem'brane.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.