The Collaborative International Dictionary of English v.0.48:

panther \pan"ther\ (p[a^]n"th[~e]r), n. [OE. pantere, F.
   panth[`e]re, L. panthera, Gr. pa`nqhr, prob. fr. Skr.
   pundr[imac]ka a tiger.]
   [1913 Webster]
   1. (Zool.) A large dark-colored variety of the leopard, by
      some Zoologists considered a distinct species. It is
      marked with large ringlike spots, the centers of which are
      darker than the color of the body.
      [1913 Webster]

   2. (Zool.) In America, the name is applied to the puma, or
      cougar, and sometimes to the jaguar.
      [1913 Webster]
      [1913 Webster]

   Panther cat (Zool.), the ocelot.

   Panther cowry (Zool.), a spotted East Indian cowry
      (Cypr[ae]a pantherina); -- so called from its color.
      [1913 Webster]

WordNet (r) 3.0 (2006):

panther cat
    n 1: nocturnal wildcat of Central America and South America
         having a dark-spotted buff-brown coat [syn: ocelot,
         panther cat, Felis pardalis]