/ Dictionary / Index C chorioallantois: Meaning and Definition of Find definitions for: cho•ri•o•al•lan•to•is 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 Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: chorioallantois (Thesaurus) chorio- choriocarcinoma Related Content Daily Word Quiz: blithesome Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language