What does "walnut" mean?

Walnut: The fruit or nut of any tree of the genus Juglans; also, the tree, and its timber. The seven or eight known species are all natives of the north temperate zone. Note: In some parts of America, especially in New England, the name walnut is given to several species of hickory (Carya), and their fruit. Ash-leaved walnut, a tree (Juglans fraxinifolia), native in Transcaucasia. -- Black walnut, a North American tree (J. nigra) valuable for its purplish brown wood, which is extensively used in cabinetwork and for gunstocks. The nuts are thick-shelled, and nearly globular. -- English, or European, walnut, a tree (J. regia), native of Asia from the Caucasus to Japan, valuable for its timber and for its excellent nuts, which are also called Madeira nuts. -- Walnut brown, a deep warm brown color, like that of the heartwood of the black walnut. -- Walnut oil, oil extracted from walnut meats. It is used in cooking, making soap, etc. -- White walnut, a North American tree (J. cinerea), bearing long, oval, thick-shelled, oily nuts, commonly called butternuts. See Butternut.