Chestnut (joke) definition

(1) (of hair) of a golden brown to reddish brown color

"A chestnut horse"

"Chestnut hair"

(2) A dark golden-brown or reddish-brown horse

(3) A small horny callus on the inner surface of a horse's leg

(4) Edible nut of any of various chestnut trees of the genus Castanea

(5) Any of several attractive deciduous trees yellow-brown in autumn; yield a hard wood and edible nuts in a prickly bur

(6) Wood of any of various chestnut trees of the genus Castanea