Aesculus hippocastanum

from WordNet (r) 3.0 (2006)

Aesculus hippocastanum
    n 1: tree having palmate leaves and large clusters of white to
         red flowers followed by brown shiny inedible seeds [syn:
         {horse chestnut}, {buckeye}, {Aesculus hippocastanum}]

from The Collaborative International Dictionary of English v.0.48

Horse-chestnut \Horse`-chest"nut\, Horsechestnut
\Horse`chest"nut\, n.
   1. (Bot.) The large nutlike seed of a species of {Aesculus}
      ({Aesculus Hippocastanum}), formerly ground, and fed to
      horses, whence the name. The seed is not considered edible
      by humans. [WordNet sense 2]
      [1913 Webster + WordNet 1.5]

   2. (Bot.) The tree itself ({Aesculus hippocastanum}), which
      was brought from Constantinople in the beginning of the
      sixteenth century, and is now common in the temperate
      zones of both hemispheres; it has palmate leaves and large
      clusters of white to red flowers followed by brown shiny
      inedible seeds. The native American species is also called
      {buckeye} and {conker}. [WordNet sense 1]
      [1913 Webster + WordNet 1.5]

from The Collaborative International Dictionary of English v.0.48

Esculin \Es*cu"lin\, n. [See {Esculic}.] (Chem.)
   A glucoside obtained from the {[AE]sculus hippocastanum}, or
   horse-chestnut, and characterized by its fine blue
   fluorescent solutions. [Written also {[ae]sculin}.]
   [1913 Webster]