Dictionary.net

The edible cotyledons of the fruit of Pistacia vera. The fruits themselves (which are also called p. nuts) are oblong drupes somewhat larger than olives, with a brittle shell containing the cotyledons. These have a greenish color and agreeable taste, and are much used as food, either dried like almonds or made into confections, etc. They contain sugar, and a fixed oil obtained from them by expression, and are a mild demulcent. They are not much employed medicinally and readily turn rancid. [Gr.]