Definition of "choroid" [cho•roid]

• The dark-brown vascular coat of the eye between the sclera and the retina. Also called choroid coat, choroid membrane. (noun)
• Resembling the chorion; membranous. (adjective)
• Of or relating to the choroid. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "In vertebrates, underneath the photoreceptors is a layer of pigment and pigment cells called the choroid the squid, cuttlefish and octopus have similar arrangements - more on this later, this layer of pigment absorbs stray light that is not caught by the photoreceptors, which might reflect back and fuzz up the image."
• "—The choroid is a thin, highly vascular membrane, of a dark brown or chocolate color, investing the posterior five-sixths of the globe; it is pierced behind by the optic nerve, and in this situation is firmly adherent to the sclera."
• "(PhysOrg. com) -- A team of scientists from the University of Toronto, the Hospital for Sick Children (SickKids) and The Children's Hospital of Los Angeles have identified a genetic mutation that plays a major role in the outcome of a paediatric brain cancer called choroid plexus carcinoma."