Source : Webster's Revised Unabridged Dictionary (1913)

Horse-chestnut \Horse`-chest"nut\, n. (Bot.)
      (a) The large nutlike seed of a species of {[AE]sculus}
          ({[AE]. Hippocastanum}), formerly ground, and fed to
          horses, whence the name.
      (b) The tree itself, which was brought from Constantinople
          in the beginning of the sixteenth century, and is now
          common in the temperate zones of both hemispheres. The
          native American species are called {buckeyes}.