Source : Webster's Revised Unabridged Dictionary (1913)

Butteris \But"ter*is\, n. [The same word as buttress, noun, in a
   different application, F. bouter to push.] (Far.)
   A steel cutting instrument, with a long bent shank set in a
   handle which rests against the shoulder of the operator. It
   is operated by a thrust movement, and used in paring the
   hoofs of horses.