iris

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The pigmented, round, contractile membrane of the eye, suspended between the cornea and lens and perforated by the pupil. It regulates the amount of light entering the eye.
• noun Any of numerous widely cultivated plants of the genus Iris, having narrow sword-shaped leaves and showy, variously colored flowers.
• noun A rainbow or rainbowlike display of colors.
• noun An iris diaphragm.

from The Century Dictionary.

• noun The root of a species of iris cultivated in India and sold in the bazaars of Calcutta to be used, like the Florentine orris-root, in perfumery and medicine.
• noun The iridescence in fractured pieces of rock-crystal.
• noun The rainbow.
• noun [capitalized] In classical mythology, the goddess of the rainbow and messenger of the gods, attached especially to Hera.
• noun [capitalized] The seventh planetoid, discovered by Hind at London in 1847.
• noun An appearance resembling a rainbow; an appearance of the hues of a rainbow, as seen in sunlit spray, the spectrum of sunlight, etc.; any iridescence.
• noun A precious stone.
• noun In anatomy, a contraetile colored curtain suspended vertically in the aqueous humor of the eye, between the cornea and the lens, separating the anterior and posterior chambers, which intercommunicate through the pupil.
• noun In entomology, the first or inner ring of an ocellated spot, adjoining the pupil, being a light-colored circle with a dark center and outer border.
• noun [capitalized] [NL. (Linnæus).] A genus of monocotyledonous plants of the natural order Irideæ, tribe Moræeæ, having the perianth 6-parted, the 3 outer divisions spreading or reflexed, and the 3 inner smaller and erect.
• noun A plant of the genus Iris.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Class. Myth.) The goddess of the rainbow, and swift-footed messenger of the gods.
• noun The rainbow.
• noun An appearance resembling the rainbow; a prismatic play of colors.
• noun (Anat.) The contractile membrane perforated by the pupil, and forming the colored portion of the eye. See Eye.
• noun (Bot.) A genus of plants having showy flowers and bulbous or tuberous roots, of which the flower-de-luce (fleur-de-lis), orris, and other species of flag are examples. See Illust. of Flower-de-luce.
• noun (Her.) See Fleur-de-lis, 2.
• noun (Zoöl.) the inner circle of an oscillated color spot.
• noun same as iris diaphragm.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun botany A plant of the genus Iris, common in the northern hemisphere, and generally having attractive blooms (Wikipedia).
• noun anatomy The contractile membrane perforated by the pupil, which adjusts to control the amount of light reaching the retina, and which forms the colored portion of the eye (Wikipedia).
• noun photography, cinematography A diaphragm used to regulate the size of a hole, especially as a way of controlling the amount of light reaching a lens.
• noun poetic A rainbow, or other colourful refraction of light.
• noun electronics A constricted opening in the path inside a waveguide, used to form a resonator.
• verb To open or close in the manner of an iris.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun plants with sword-shaped leaves and erect stalks bearing bright-colored flowers composed of three petals and three drooping sepals
• noun diaphragm consisting of thin overlapping plates that can be adjusted to change the diameter of a central opening
• noun muscular diaphragm that controls the size of the pupil which in turn controls the amount of light that enters the eye; it forms the colored portion of the eye