Pronunciation: (spīn),[key] —n. 1. the spinal or vertebral column; backbone.
2. any backbonelike part.
3. a stiff, pointed process or appendage on an animal, as a quill of a porcupine, or a sharp, bony ray in the fin of a fish.
4. something, as a quality or trait, that constitutes a principal strength; resolution; stamina; backbone: a situation that would test a person's spine. 5. a ridge, as of ground or rock.
6. a sharp-pointed, hard or woody outgrowth on a plant; thorn.
7. Bookbinding.the back of a book cover or binding, usually indicating the title and author.