spine

noun

1. The series of bones situated at the back from the head to the pelvis of a person, or from the head to the tail of an animal; backbone, vertebral column.
2. Something resembling a backbone, such as a ridge, or a long, central structure from which other structures radiate.
3. A pointed, fairly rigid protuberance or needle-like structure on an animal, shell, or plant.
4. The heartwood of trees.