The Collaborative International Dictionary of English v.0.48:

Jaguar \Ja*guar"\, n. [Braz. yago['a]ra: cf. & Pg. jaguar.]
   (Zool.)
   A large and powerful feline animal (Panthera onca, formerly
   Felis onca), ranging from Texas and Mexico to Patagonia. It
   is usually brownish yellow, with large, dark, somewhat
   angular rings, each generally inclosing one or two dark
   spots. It is chiefly arboreal in its habits. It is also
   called the panther and the American tiger.
   [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

jaguar
    n 1: a large spotted feline of tropical America similar to the
         leopard; in some classifications considered a member of the
         genus Felis [syn: jaguar, panther, Panthera onca,
         Felis onca]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "jaguar":
   Dalmatian, Leo, Siberian tiger, antigorite, bobcat, butterfly,
   candy cane, cat-a-mountain, catamount, chameleon, cheetah,
   chrysotile, confetti, cougar, crazy quilt, firedog, harlequin,
   iris, leopard, lion, lynx, mackerel, mackerel sky, marble,
   marbled paper, moire, mother-of-pearl, mountain lion, nacre,
   ocelot, opal, ophite, painter, panther, patchwork quilt, peacock,
   puma, rainbow, serpentine, serpentine marble, shot silk, simba,
   spectrum, tiger, tortoise shell, wildcat, zebra