buckthorn

noun6

1. •
   Any of several, often thorny shrubs or small trees.
2. •
   the buckthorn family (Rhamnaceae),
3. •
   especially genus Rhamnus,
4. •
   especially common buckthorn or purging buckthorn (Rhamnus cathartica).
5. •
   also alder buckthorn (Frangula), especially Frangula alnus.
6. •
   sea buckthorn (Hippophae, in family Elaeagnaceae).