1a North American tree or shrub related to the horse chestnut, with showy yellow, red, or white flowers.
- Genus Aesculus, family Hippocastanaceae: several species, including the Ohio buckeye (A. glabra), with yellow flowers and prickly fruit husks
2 (also buckeye butterfly) an orange and brown New World butterfly with conspicuous eyespots on the wings.
- Junonia coenia, subfamily Nymphalinae, family Nymphalidae
3 (Buckeye) US informal a native of the state of Ohio.
[from the name given to the state, with reference to the abundance of buckeye trees]
4 (also buckeye coupling) a kind of automatic coupling for railroad rolling stock.
[named after the Buckeye Steel Castings Company, Columbus, Ohio]