from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The pigment sensitive to red light in the retinal rods of the eyes, consisting of opsin and retinene. Also called visual purple.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A light-sensitive pigment in the rod cells of the retina; it consists of an opsin protein bound to the carotenoid retinal
from the GNU version of the Collaborative International Dictionary of English
- n. The visual purple. See under visual.
from The Century Dictionary and Cyclopedia
- n. Visual purple; a pigment found in the outer segments of the retinal rods.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a red photopigment in the retinal rods of vertebrates; dissociates into retinene by light
rhod(o)- + Greek opsis, sight; see -opsis + -in.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Ancient Greek ῥόδον (rhodon, "rose"), due to its pinkish color, and ὄψις (opsis, "sight"). (Wiktionary)