aculeus
/əˈkjuːliəs/
noun
- A sharp, pointed structure like a spine or prickle, especially on a plant or animal.
- Biologists studied the aculeus of the stingray to understand how it delivers venom.
- The cactus is covered in tiny aculei that can easily pierce the skin.
- The rose stem's aculeus is actually a modified part of the plant's outer layer.