Source : Webster's Revised Unabridged Dictionary (1913)

Bighorn \Big"horn`\, n. (Zo["o]l.)
   The Rocky Mountain sheep ({Ovis or Caprovis montana}).

Source : WordNet®

Bighorn
     n 1: a river that flows from central Wyoming to the Yellowstone
          River in southern Montana [syn: {Bighorn River}]
     2: wild sheep of mountainous regions of western North America
        having massive curled horns [syn: {bighorn sheep}, {cimarron},
         {Rocky Mountain bighorn}, {Rocky Mountain sheep}, {Ovis
        canadensis}]