The Collaborative International Dictionary of English v.0.48:

Capricorn \Cap"ri*corn\, n. [L. capricornus; caper goat + cornu
   horn: cf. F. capricorne.]
   1. (Astron.) The tenth sign of zodiac, into which the sun
      enters at the winter solstice, about December 21. See
      Tropic.
      [1913 Webster]

            The sun was entered into Capricorn.   --Dryden.
      [1913 Webster]

   2. (Astron.) A southern constellation, represented on ancient
      monuments by the figure of a goat, or a figure with its
      fore part like a fish.
      [1913 Webster]

   Capricorn beetle (Zool.), any beetle of the family
      Carambucid[ae]; one of the long-horned beetles. The
      larv[ae] usually bore into the wood or bark of trees and
      shrubs and are often destructive. See Girdler, Pruner.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Capricorn
    n 1: (astrology) a person who is born while the sun is in
         Capricorn [syn: Capricorn, Goat]
    2: a faint zodiacal constellation in the southern hemisphere;
       between Sagittarius and Aquarius [syn: Capricornus,
       Capricorn]
    3: the tenth sign of the zodiac; the sun is in this sign from
       about December 22 to January 19 [syn: Capricorn, Capricorn
       the Goat, Goat]