Source : Webster's Revised Unabridged Dictionary (1913)

Canon bone \Can"on bone`\ [F. canon, fr. L. canon a rule. See
   {canon}.] (Anat.)
   The shank bone, or great bone above the fetlock, in the fore
   and hind legs of the horse and allied animals, corresponding
   to the middle metacarpal or metatarsal bone of most mammals.
   See {Horse}.