Spine

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

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.