Spine

Part of speech: noun (n.)

1. A sharp appendage to any of a plant; a thorn.

2. A rigid and sharp projection upon any part of an animal.

3. One of the rigid and undivided fin rays of a fish.

4. The backbone, or spinal column, of an animal; -- so called from the projecting processes upon the vertebræ.

5. Anything resembling the spine or backbone; a ridge.