- any of the stiff, sharp-pointed, superficial emergences on a plant, as on a rose, thistle, or cactus
- a sharp process of bone
- any of the sharp, stiff projections on the bodies of certain animals, as the quill of a porcupine or a ray of a fish's fin
- anything resembling either of these projections
- the spinal column; backbone
- anything regarded as resembling a backbone, as
- a ridge of ground, crest of a hill, etc.
- the part of a bound book covering the backbone, and usually bearing the title and author's name
- courage, willpower, etc.
Origin of spineMiddle English from Old French espine from Classical Latin spina, thorn, prickle, backbone: see spike