iris

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. 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.
2. n. Any of numerous plants of the genus Iris, having narrow sword-shaped leaves and showy, variously colored flowers.
3. n. A rainbow or rainbowlike display of colors.
4. n. An iris diaphragm.

Century Dictionary and Cyclopedia

1. n. The rainbow.
2. n. [capitalized] In classical mythology, the goddess of the rainbow and messenger of the gods, attached especially to Hera. She was considered as a radiant maiden borne in swift flight on golden wings, and was often represented with the herald's attributes of Hermes—the talaria and caduceus. Hence sometimes used for any messenger.
3. n. [capitalized] The seventh planetoid, discovered by Hind at London in 1847.
4. n. 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.
5. n. A precious stone.
6. n. 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. The iris gives the color to the eye, by the presence or absence of pigment, and regulates, by contraction and dilatation of its aperture, the amount of light admitted to the eye. The movements of the iris, and consequently the size and shape of the pupil, are effected by two sets of muscular fibers, circular and radiating. The circular fibers which contract the pupil are under the control of the third cranial nerve, while the innervation of the radiating fibers is through the cervical sympathetic. The pupil contracts when the retina is stimulated by light, and on convergence or on accommodation. The pupil dilates on stimulation of the skin. When its contraction is uniform, the pupil always remains circular, as in man; in other cases, as that of the cat, the pupil is a narrow slit when contracted, though circular when dilated; in others, again, the pupil has a more constant oval, elliptical, oblong, or other shape. Muscular action of the iris is usually automatic, depending upon the stimulus of light; but many animals, as birds, have striped and probably voluntary iridian muscles. Some drugs affect the iris powerfully and specifically: thus, opium contracts and belladonna dilates the pupil. Great as is the range of color in the human iris, from light-bluish and grayish tints through all shades of brown to blackish, it is slight in comparison with that of birds, where not only the browns, but bright reds, greens, and blues are found, and sometimes pure white. The iris of albinos is generally pink, being devoid of pigment, and consequently displaying the color of the delicate blood-vessels. The pupil normally appears black, the dark coat of the back of the eyeball being seen through this aperture. See cuts under eye.
7. n. 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.
8. n. [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. The pod is 3- to 6-angled. They are perennial herbs with sword-shaped or grassy leaves and generally large and showy purple, yellow, or white flowers. About 100 species are known, natives of Europe, northern Africa, and temperate Asia and America. They are widely known in cultivation under the name of fleur-de-lis (flower-deluce), I. Germanica being the common cultivated form. The wild species are very generally known in America as blue flag, I. versicolor being the larger blue flag and I. Virginica the slender blue flag. I. verna of the eastern United States is the dwarf iris, and I. cristata of nearly the same range is the crested dwarf iris. I. Pseudacorus of Europe and Russian Asia is the yellow iris or yellow flag. The roots possess astringent qualities, and the seeds when roasted are used in Great Britain as a substitute for coffee. I. fætidissima of western Europe is the fetid iris, gladden, or roast-beef plant. The orris-root of commerce is supplied by I. florentina. This root possesses cathartic and emetic properties, and from its agreeable odor is also used in making tooth-and hair-powders. Six extinct species of Iris have been described from the Tertiary deposits of Europe (one in Spitzbergen), and several allied forms from lower formations, under thenames Iridium and Irites.
9. n. A plant of the genus Iris.
10. n. 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.
11. n. The iridescence in fractured pieces of rock-crystal. When the fractures are cut out with the upper crystal itself and polished, they show a beautiful play of color. The name is also applied to rock-crystal and the cheaper stones to which color is applied by means of a coating on the back to produce the effect of a play of colors. A similar effect is produced by cementing various colored glasses together and then coating them.

Wiktionary

1. n. A plant of the genus Iris, common in the northern hemisphere, and generally having attractive blooms.
2. n. 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.
3. n. A diaphragm used to regulate the size of a hole, especially as a way of controlling the amount of light reaching a lens.
4. n. A rainbow, or other colourful refraction of light.
5. v. To open or close in the manner of an iris.

GNU Webster's 1913

1. n. The goddess of the rainbow, and swift-footed messenger of the gods.
2. n. The rainbow.
3. n. An appearance resembling the rainbow; a prismatic play of colors.
4. n. The contractile membrane perforated by the pupil, and forming the colored portion of the eye. See Eye.
5. n. 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.
6. n. See Fleur-de-lis, 2.
7. n. the inner circle of an oscillated color spot.
8. n. same as iris diaphragm.

WordNet 3.0

1. n. plants with sword-shaped leaves and erect stalks bearing bright-colored flowers composed of three petals and three drooping sepals
2. n. diaphragm consisting of thin overlapping plates that can be adjusted to change the diameter of a central opening
3. n. 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