The Collaborative International Dictionary of English v.0.48:

Purple \Pur"ple\, n.; pl. Purples. [OE. purpre, pourpre, OF.
   purpre, porpre, pourpre, F. pourpre, L. purpura purple fish,
   purple dye, fr. Gr. ? the purple fish, a shell from the
   purple dye was obtained, purple dye; cf. ? dark (said of the
   sea), purple, ? to grow dark (said of the sea), to be
   troubled; perh. akin to L. furere to rage, E. fury: cf. AS.
   purpure. Cf. Porphyry, Purpure.]
   1. A color formed by, or resembling that formed by, a
      combination of the primary colors red and blue.
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            Arraying with reflected purple and gold
            The clouds that on his western throne attend. --
                                                  Milton.
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   Note: The ancient words which are translated purple are
         supposed to have been used for the color we call
         crimson. In the gradations of color as defined in art,
         purple is a mixture of red and blue. When red
         predominates it is called violet, and when blue
         predominates, hyacinth.
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   2. Cloth dyed a purple color, or a garment of such color;
      especially, a purple robe, worn as an emblem of rank or
      authority; specifically, the purple rode or mantle worn by
      Roman emperors as the emblem of imperial dignity; as, to
      put on the imperial purple.
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            Thou shalt make the tabernacle with ten curtains of
            fine twined linen, and purple, and scarlet. --Ex.
                                                  xxvi. 1.
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   3. Hence: Imperial sovereignty; royal rank, dignity, or
      favor; loosely and colloquially, any exalted station;
      great wealth. "He was born in the purple." --Gibbon.
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   4. A cardinalate. See Cardinal.
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   5. (Zool.) Any species of large butterflies, usually marked
      with purple or blue, of the genus Basilarchia (formerly
      Limenitis) as, the banded purple (Basilarchia
      arthemis). See Illust. under Ursula.
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   6. (Zool.) Any shell of the genus Purpura.
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   7. pl.(Med.) See Purpura.
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   8. pl. A disease of wheat. Same as Earcockle.
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   Note: Purple is sometimes used in composition, esp. with
         participles forming words of obvious signification; as,
         purple-colored, purple-hued, purple-stained,
         purple-tinged, purple-tinted, and the like.
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   French purple. (Chem.) Same as Cudbear.

   Purple of Cassius. See Cassius.

   Purple of mollusca (Zool.), a coloring matter derived from
      certain mollusks, which dyes wool, etc., of a purple or
      crimson color, and is supposed to be the substance of the
      famous Tyrian dye. It is obtained from Ianthina, and from
      several species of Purpura, and Murex.

   To be born in the purple, to be of princely birth; to be
      highborn.
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