Source : Webster's Revised Unabridged Dictionary (1913)

Canvasback \Can"vas*back`\, n. (Zo["o]l.)
   A Species of duck ({Aythya vallisneria}), esteemed for the
   delicacy of its flesh. It visits the United States in autumn;
   particularly Chesapeake Bay and adjoining waters; -- so named
   from the markings of the plumage on its back.

Source : WordNet®

canvasback
     n : North American wild duck valued for sport and food [syn: {canvasback
         duck}, {Aythya valisineria}]