spine

(noun) the series of vertebrae forming the axis of the skeleton and protecting the spinal cord. Synonyms: spinal column, vertebral column, backbone, back, rachis. Examples: "The fall broke his back."

(noun) any sharply pointed projection. Synonyms: spur, acantha.

(noun) a small sharp-pointed tip resembling a spike on a stem or leaf. Synonyms: thorn, prickle, pricker, sticker, spikelet.

(noun) the part of a book's cover that encloses the inner side of the book's pages and that faces outward when the book is shelved. Synonyms: backbone. Examples: "The title and author were printed on the spine of the book."

(noun) a sharp rigid animal process or appendage; as a porcupine quill or a ridge on a bone or a ray of a fish fin.