iris

Etymology

From Middle English [Term?], from Latin īris, from Ancient Greek ἶρις (îris, “rainbow”), possibly from a derivative of Proto-Indo-European *w(e)ih₁-ro- (“a twist, thread, cord, wire”), from *weh₁y- (“to turn, twist, weave, plait”). If so, it would be cognate to English wire.

noun

1. (botany) A plant of the genus Iris, common in the northern hemisphere, and generally having attractive blooms.
2. (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.
3. (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.
4. (poetic) A rainbow, or other colourful refraction of light.
5. (electronics) A constricted opening in the path inside a waveguide, used to form a resonator.
6. (zoology) The inner circle of an oscillated color spot.

verb

1. (of an aperture, lens, or door) To open or close in the manner of an iris.
2. (literary) To cause (something) to shine with the colours of the rainbow; to make iridescent.
   Pure, transparent, glistening in the sun, and irised by a thousand hues, which float and wave and spread in graceful and ceaseless motion on its surface! 1834, Jacob Abbott, chapter 1, in The Corner-Stone, Boston: William Peirce, page 31
   The sun as it comes indoors out of space Has left a rainbow irising each glass— A refraction, caught then multiplied From the crystal tied within our window, 1987, Charles Tomlinson, “Winter Journey”, in The Return, Oxford University Press, page 35