chorion
noun
cho·ri·on
ˈkȯr-ē-ˌän 
: the highly vascular outer embryonic membrane of reptiles, birds, and mammals that in placental mammals is associated with the allantois in the formation of the placenta
Examples of chorion in a Sentence
Recent Examples on the Web
If the split is delayed, usually a week or so after conception, the processes of growing a placenta, chorion, and amniotic sac are already underway.
—
Pamela Prindle Fierro, Parents, 30 July 2024
This is essentially a blood clot that can occur when the outermost membrane surrounding the embryo (the chorion) separates a little from the uterine wall, allowing some blood to pool in that space between the two.
—Amy Marturana, SELF, 28 Dec. 2018
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Pamela Prindle Fierro, Parents, 30 July 2024
This is essentially a blood clot that can occur when the outermost membrane surrounding the embryo (the chorion) separates a little from the uterine wall, allowing some blood to pool in that space between the two.
—Amy Marturana, SELF, 28 Dec. 2018
Cite this Entry
“Chorion.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/chorion. Accessed 3 Nov. 2025.
Copy CitationKids Definition
chorion
noun
cho·ri·on
ˈkōr-ē-ˌän
ˈkȯr-
: the outer membrane that surrounds the embryo of reptiles, birds, and mammals and that in mammals with a placenta contributes to the formation of the placenta
chorionic
adjective
ˌkōr-ē-ˈän-ik
ˌkȯr-
Medical Definition
chorion
noun
cho·ri·on
ˈkōr-ē-ˌän, ˈkȯr-
Love words? Need even more definitions?
Merriam-Webster unabridged
Share