spinen.[L. spina thorn, the spine; akin to spica a point: cf. OF. espine, F. pine. Cf. Spike, Spinet a musical instrument, Spinny.]1. (Bot.) A sharp appendage to any of a plant; a thorn.()2. (Zol.) A rigid and sharp projection upon any part of an animal.()3. (Anat.) The backbone, or spinal column, of an animal; -- so called from the projecting processes upon the vertebr.()4. Anything resembling the spine or backbone; a ridge.()