A rainbow, or other colourful refraction of light.
A plant of the genus Iris, common in the northern hemisphere, and generally having attractive blooms (See Iris (plant) on Wikipedia.Wikipedia).
A constricted opening in the path inside a waveguide, used to form a resonator.
A diaphragm used to regulate the size of a hole, especially as a way of controlling the amount of light reaching a lens.
The inner circle of an oscillated color spot.
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 (See Iris (anatomy) on Wikipedia.Wikipedia).
To open or close in the manner of an iris.
To cause (something) to shine with the colours of the rainbow; to make iridescent.
The anadromous form of the rainbow trout, Oncorhynchus mykiss.
The ruddy duck.