spine Definition

spine
noun

1. In vertebrates: the flexible bony structure, consisting of a column of vertebrae connected by cartilage discs, that surrounds and protects the spinal cord and articulates with the skull, ribs and pelvic girdle.

Thesaurus: backbone, vertebrae, spinal column.
2. The narrow middle section in the cover of a book that hides the part where the pages are fastened in and which often carries details of the title and/or author.
3. In certain plants and animals, eg cacti, hedgehogs, porcupines, etc: one of many sharply pointed structures that protect the plant or animal against predators.

Thesaurus: thorn, spike, barb, needle, quill, thistle.
4. colloq
Courage; strength of character.
Example: hasn't got the spine to answer back

Etymology: 15c: from French espine, from Latin spina thorn, prickle or backbone.