buck·eye / ˈbəkˌī/ • n. 1. a North American tree or shrub (genus Aesculus, family Hippocastanaceae), related to the horse chestnut, with showy yellow, red, or white flowers. 2. (also buckeye butterfly) an orange and brown New World butterfly (Junonia coenia, family Nymphalidae) with conspicuous eyespots on the wings. 3. (Buckeye) inf. a native of the state of Ohio (with reference to Ohio's abundance of buckeye trees).

buckeye See AESCULUS and HIPPOCASTANACEAE.