chestnut

1. A tree or shrub of the genus Castanea.
2. The nut of this tree or shrub.
3. A dark, reddish-brown colour, as seen on the fruit of the chestnut tree.
4. A reddish-brown horse.
5. The wood of a chestnut tree.
6. 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").
7. 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.
8. The horse-chestnut.

adjective

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