English walnut

1. A Eurasian tree (Juglans regia) cultivated in southern Europe and California for its valuable wood and its large, edible nuts.
2. The nut of this tree.

The United States (mainly California) is the world's leading producer of the English walnut (also called Persian walnut). It's grown in several other countries including China, France, India, Iran, Turkey and Yugoslavia. The English walnut has a wrinkled, tan-colored shell that encloses two large, double-lobed halves. Its sweet flavor makes it a delicious choice for out-of-hand eating, as well as a popular addition for all manner of foods sweet and savory. English walnuts are used to produce walnut oil; they also come in candied and pickled forms. They're available prepackaged or in bulk. English walnuts are a potent source of Omega-3 oils (see fats and oils). See also nuts; walnut.

The noun has 2 meanings:

Meaning #1: Eurasian walnut valued for its large edible nut and its hard richly figured wood; widely cultivated
  Synonyms: English walnut tree, Circassian walnut, Persian walnut, Juglans regia

Meaning #2: nut with a wrinkled two-lobed seed and hard but relatively thin shell; widely used in cooking