cho·roid / ˈkôrˌoid/ (also cho·ri·oid / ˈkôrēˌoid/ ) • adj. resembling the chorion, particularly in containing many blood vessels.• n. (also choroid coat) the pigmented vascular layer of the eyeball between the retina and the sclera.DERIVATIVES: cho·roi·dal / kəˈroidl/ adj. .

choroid A pigmented layer, rich in blood vessels, that lies between the retina and the sclerotic of the vertebrate eye. At the front of the eye the choroid is modified to form the ciliary body and the iris.

choroid (ko-roid) n. the layer of the eyeball between the retina and the sclera. It contains blood vessels and a pigment that absorbs excess light and so prevents blurring of vision. See eye.
—choroidal (kŏ-roid-ăl) adj.

choroid In the eye of a vertebrate, a layer of tissue lying immediately outside the retina that contains pigment and blood vessels.