The Collaborative International Dictionary of English v.0.48:

Phaeton \Pha"["e]*ton\ (f[=a]"[-e]*t[o^]n), n. [F. pha['e]ton a
   kind of carriage, fr. Pha['e]thon Pha["e]thon, the son of
   Helios. See Pha["e]thon.]
   1. A four-wheeled carriage (with or without a top), open, or
      having no side pieces, in front of the seat. It is drawn
      by one or two horses.
      [1913 Webster]

   2. See Pha["e]thon.
      [1913 Webster]

   3. (Zool.) A handsome American butterfly (Euphydryas
      Pha["e]ton syn. Melit[ae]a Pha["e]ton). The upper side
      of the wings is black, with orange-red spots and marginal
      crescents, and several rows of cream-colored spots; --
      called also Baltimore.
      [1913 Webster]

WordNet (r) 3.0 (2006):

phaeton
    n 1: large open car seating four with folding top [syn: touring
         car, phaeton, tourer]