chestnut

An edible nut (technically a fruit) of the Spanish chestnut or sweet chestnut tree (Castanea sativa); also (chiefly preceded by a descriptive word), a nut from a related shrub or tree; or a similar nut from an unrelated plant.

In full chestnut tree: the shrub or tree that bears this nut, the Spanish chestnut or sweet chestnut (Castanea sativa); also (chiefly preceded by a descriptive word), a shrub or tree of the genus Castanea.

Wood of a chestnut tree.

Short for horse chestnut (“any of several tree species of the genus Aesculus, especially Aesculus hippocastanum; the fruit of such a tree”).

A dark, reddish-brown colour, like that of chestnut fruit (noun sense 1).

A horse with a reddish-brown coat.

An oval or round horny plate located on the inner side of the leg of a horse or other equines, which is thought by some people to correspond with the thumbnail of other animals.

Chiefly in old chestnut: a joke, meme, phrase, ploy, etc. which has been repeated so often as to have grown ineffective or tiresome; a cliché.