Source : Webster's Revised Unabridged Dictionary (1913)

Pistache \Pis*tache"\, n. [OE. pistace, fr. F. pistache. See
   {Pistachio}.] (Bot.)
   The anacardiaceous tree {Pistacia vera}, which yields the
   pistachio nut; also, the nut itself and the flavoring extract
   prepared from it.

Pistachio \Pis*ta"chio\, n. [It. pistacchio (cf. Sp. pistacho,
   F. pistache), fr. L. pistacium, Gr. ?, ?, fr. Per. pistah.
   Cf. {Fistinut}.] (Bot.)
   The nut of the {Pistacia vera}, a tree of the order
   {Anacardiace[ae]}, containing a kernel of a pale greenish
   color, which has a pleasant taste, resembling that of the
   almond, and yields an oil of agreeable taste and odor; --
   called also {pistachio nut}. It is wholesome and nutritive.
   The tree grows in Arabia, Persia, Syria, and Sicily. [Written
   also {pistachia}.]

Source : WordNet®

Pistacia vera
     n : small tree of southern Europe and Asia Minor bearing small
         hard-shelled nuts [syn: {pistachio}, {pistachio tree}]