Source : Webster's Revised Unabridged Dictionary (1913)

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}.]

Source : WordNet®

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