The Collaborative International Dictionary of English v.0.48:

Violet \Vi"o*let\, n. [F. violette a violet (cf. violet
   violet-colored), dim. of OF. viole a violet, L. viola; akin
   to Gr. ?. Cf. Iodine.]
   1. (Bot.) Any plant or flower of the genus Viola, of many
      species. The violets are generally low, herbaceous plants,
      and the flowers of many of the species are blue, while
      others are white or yellow, or of several colors, as the
      pansy (Viola tricolor).
      [1913 Webster]

   Note: The cultivated sweet violet is Viola odorata of
         Europe. The common blue violet of the eastern United
         States is Viola cucullata; the sand, or bird-foot,
         violet is Viola pedata.
         [1913 Webster]

   2. The color of a violet, or that part of the spectrum
      farthest from red. It is the most refrangible part of the
      spectrum.
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   3. In art, a color produced by a combination of red and blue
      in equal proportions; a bluish purple color. --Mollett.
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   4. (Zool.) Any one of numerous species of small
      violet-colored butterflies belonging to Lycaena, or
      Rusticus, and allied genera.
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      [1913 Webster]

   Corn violet. See under Corn.

   Dame's violet. (Bot.) See Damewort.

   Dogtooth violet. (Bot.) See under Dogtooth.

   Water violet (Bot.), an aquatic European herb (Hottonia
      palustris) with pale purplish flowers and pinnatifid
      leaves.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Water violet \Wa"ter vi"o*let\ (Bot.)
   See under Violet.
   [1913 Webster]

WordNet (r) 3.0 (2006):

water violet
    n 1: featherfoil of Europe and western Asia having submerged and
         floating leaves and violet flowers [syn: water violet,
         Hottonia palustris]