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: Webster's Revised Unabridged Dictionary (1913)