The Collaborative International Dictionary of English v.0.48:

Bucentaur \Bu*cen"taur\, n. [Gr. boy^s ox + ke`ntayros centaur.]
   1. A fabulous monster, half ox, half man.
      [1913 Webster]

   2. [It. bucentoro.] The state barge of Venice, used by the
      doge in the ceremony of espousing the Adriatic.
      [1913 Webster]