[kawr-ee-on, kohr-]
  1. Embryology. the outermost of the extraembryonic membranes of land vertebrates, contributing to the formation of the placenta in the placental mammals.
  2. Zoology. the membrane around the eggs of certain insects, secreted by cells of the ovary.

Origin of chorion

1535–45; < New Latin < Greek chórion membrane enclosing the fetus
Related formscho·ri·on·ic, cho·ri·al, adjectivesub·cho·ri·on·ic, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for chorion

Historical Examples of chorion

British Dictionary definitions for chorion


  1. the outer of two membranes that form a sac around the embryonic reptile, bird, or mammal: contributes to the placenta in mammalsSee also amnion
Derived Formschorionic or chorial, adjective

Word Origin for chorion

C16: from Greek khorion afterbirth
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for chorion

"outer membrane of the fetus," 1540s, medical Latin, from Greek khorion "membrane enclosing the fetus, afterbirth," perhaps from PIE *ghere- "gut, entrail" (see yarn).

Online Etymology Dictionary, © 2010 Douglas Harper

chorion in Medicine


  1. The outer membrane enclosing the embryo in reptiles, birds, and mammals. In placental mammals it contributes to the development of the placenta.
Related formscho′ri•onic (-ŏnĭk) adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

chorion in Science


  1. The outer membrane that encloses the embryo of a reptile, bird, or mammal. In mammals, the chorion contributes to the development of the placenta.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.