The Collaborative International Dictionary of English v.0.48:

Tropic \Trop"ic\, n. [F. tropique, L. tropicus of or belonging
   to a turn, i. e., of the sun, Gr. ? of the solstice, ? (sc.
   ?) the tropic or solstice, fr. ? to turn. See Trope.]
   1. (Astron.) One of the two small circles of the celestial
      sphere, situated on each side of the equator, at a
      distance of 23[deg] 28[min], and parallel to it, which the
      sun just reaches at its greatest declination north or
      south, and from which it turns again toward the equator,
      the northern circle being called the Tropic of Cancer,
      and the southern the Tropic of Capricorn, from the names
      of the two signs at which they touch the ecliptic.
      [1913 Webster]

   2. (Geog.)
      (a) One of the two parallels of terrestrial latitude
          corresponding to the celestial tropics, and called by
          the same names.
      (b) pl. The region lying between these parallels of
          latitude, or near them on either side.
          [1913 Webster]

                The brilliant flowers of the tropics bloom from
                the windows of the greenhouse and the saloon.
                                                  --Bancroft.
          [1913 Webster]

WordNet (r) 3.0 (2006):

Tropic of Capricorn
    n 1: a line of latitude about 23 degrees to the south of the
         equator