- Pecan tree - An American tree of the genus Carya, of which there are
several species. The shagbark is the C. alba, and has a very rough
bark; it affords the hickory nut of the markets. The pignut, or brown
hickory, is the C. glabra. The swamp hickory is C. amara, having a nut
whose shell is very thin and the kernel bitter.