- any of several, sometimes thorny trees or shrubs belonging to the genus Rhamnus, especially R. frangula, the bark of which is used in medicine.
- a tree or shrub belonging to the genus Bumelia, of the sapodilla family, especially B. lycioides, a thorny tree having elliptic leaves and large clusters of white flowers, common in the southern and part of the central U.S.
- any of several thorny small-flowered shrubs of the genus Rhamnus, esp the Eurasian species R. cathartica, whose berries were formerly used as a purgative: family Rhamnaceae
