spine

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The spinal column of a vertebrate.
• noun Zoology Any of various pointed projections, processes, or appendages of animals.
• noun A strong, sharp-pointed outgrowth derived from a leaf or leaf part.
• noun Any of various similar sharp structures, such as a thorn.
• noun Something that resembles or suggests a backbone, as.
• noun The hinged back of a book.
• noun The crest of a ridge.
• noun Strength of character; courage or willpower.

from The Century Dictionary.

• noun One of the quills of a harpsichord or spinet.
• noun Specifically, a sharp, columnar mass of solidified lava which was forced upward to a height of over 1,000 feet above the summit of Mount Pelée, Martinique, in 1903. See volcano, 1. It constituted a new phenomenon in vulcanology. See cut under cumulo-volcano.
• noun In botany, a stiff sharp-pointed process, containing more or less woody tissue, and originating in the degeneracy or modification of some organ.
• noun The backbone; the rachis, spina, or spinal column of a vertebrate.
• noun A name of some part in various animals.
• noun In much., any longitudinal ridge; a fin.
• noun In lace-making, a raised projection from the cordonnet: one of the varieties of pinwork; especially, one of many small points that project outward from the edge of the lace, forming a sort of fringe.
• noun The duramen or heartwood of trees: a ship-builders' term. See duramen.
• noun and hemal.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Bot.) A sharp appendage to any of a plant; a thorn.
• noun A rigid and sharp projection upon any part of an animal.
• noun One of the rigid and undivided fin rays of a fish.
• noun (Anat.) The backbone, or spinal column, of an animal; -- so called from the projecting processes upon the vertebræ.
• noun Anything resembling the spine or backbone; a ridge.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A person or thing's backbone; the series of bones collectively from one's (literal or figurative) head to tail or pelvis.
• noun A rigid, pointed surface protuberance or needle-like structure on an animal, shell, or plant.
• noun Courage or assertiveness.
• noun The narrow, bound edge of a book.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• 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
• noun a small sharp-pointed tip resembling a spike on a stem or leaf
• noun the series of vertebrae forming the axis of the skeleton and protecting the spinal cord
• 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
• noun any sharply pointed projection