SPINE

noun a sharp appendage to any of a plant; a thorn.

2. spine ·noun one of the rigid and undivided fin rays of a fish.

3. spine ·noun anything resembling the spine or backbone; a ridge.

4. spine ·noun a rigid and sharp projection upon any part of an animal.

5. spine ·noun the backbone, or spinal column, of an animal;

— so called from the projecting processes upon the vertebrae.