Source : Webster's Revised Unabridged Dictionary (1913)

Saddleback \Sad"dle*back`\, n.
   1. Anything saddle-backed; esp., a hill or ridge having a
      concave outline at the top.

   2. (Zo["o]l.)
      (a) The harp seal.
      (b) The great blackbacked gull ({Larus marinus}).
      (c) The larva of a bombycid moth ({Empretia stimulea})
          which has a large, bright green, saddle-shaped patch
          of color on the back.