Chestnut  —n. 1 a glossy hard brown edible nut. B tree bearing it. 2 = *horse chestnut. 3 wood of any chestnut. 4 horse of a reddish-brown colour. 5 colloq. Stale joke etc. 6 reddish-brown. —adj. Reddish-brown. [greek kastanea nut]