Spine \Spine\, n. [L. spina thorn, the spine; akin to spica a point: cf. OF. espine, F. ['e]pine. Cf. Spike, Spinet a musical instrument, Spinny.]

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

2. (Zo["o]l.)
   (a) A rigid and sharp projection upon any part of an animal.
   (b) One of the rigid and undivided fin rays of a fish.

3. (Anat.) The backbone, or spinal column, of an animal; -- so called from the projecting processes upon the vertebr[ae].

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

Source: Webster's Revised Unabridged Dictionary (1913)