The Collaborative International Dictionary of English v.0.48:

Iris \I"ris\, n.; pl. E. Irises, L. Irides. [L. iris,
   iridis, the goddess, Gr. ?, ?, the rainbow, iris of the eye,
   the plant Iris. Cf. Orris.]
   1. (Class. Myth.) The goddess of the rainbow, and
      swift-footed messenger of the gods. --Shak.
      [1913 Webster]

   2. The rainbow. --Sir T. Browne.
      [1913 Webster]

   3. An appearance resembling the rainbow; a prismatic play of
      colors. --Tennyson.
      [1913 Webster]

   4. (Anat.) The contractile membrane perforated by the pupil,
      and forming the colored portion of the eye. See Eye.
      [1913 Webster]

   5. (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.
      [1913 Webster]

   6. (Her.) See Fleur-de-lis, 2.
      [1913 Webster]

   7. (Zool.) the inner circle of an oscillated color spot.
      [Webster 1913 Suppl.]

   8. same as iris diaphragm.
      [PJC]