Available Definitions:
1) n. - A sharp appendage to any of a plant; a thorn.
2) n. - A rigid and sharp projection upon any part of an animal.
3) n. - One of the rigid and undivided fin rays of a fish.
4) n. - The backbone, or spinal column, of an animal; -- so called from the projecting processes upon the vertebrae.
5) n. - Anything resembling the spine or backbone; a ridge.