What does "pistachio" mean?

Pistachio: The nut of the Pistacia vera, a tree of the order Anacardiaceæ, 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.]