Meaning

• A tree or shrub of the genus Castanea.

• The nut of this tree or shrub.

• A dark, reddish-brown colour, as seen on the fruit of the chestnut tree.

• A reddish-brown horse.

• The wood of a chestnut tree.

• An old joke; a worn-out meme, phrase, ploy, etc. so often repeated as to have grown tiresome or ineffective (often in the phrase "old chestnut").

• A round or oval horny plate found on the inner side of the leg of a horse or other animal, similar to a birthmark on a human.

• The horse-chestnut.

Meaning

• Of a deep reddish-brown colour, like that of a chestnut.