walnutn.[OE. walnot, AS. wealh-hnutu a Welsh or foreign nut, a walnut; wealh foreign, strange, n., a Welshman, Celt (akin to OHG. Walh, properly, a Celt, from the name of a Celtic tribe, in L. Volcae) + hnutu a nut; akin to D. walnoot, G. walnuss, Icel. valhnot, Sw. valnt, Dan valnd. See Nut, and cf. Welsh.] (Bot.) 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.()()()Ash-leaved walnut, a tree (Juglans fraxinifolia), native in Transcaucasia. -- Black walnut, a North American tree (Juglans 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 walnut, or European walnut, a tree (Juglans 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 (Juglans cinerea), bearing long, oval, thick-shelled, oily nuts, commonly called butternuts. See Butternut.()