Back″bone″ (–bōn′), n. [2d back, n. + bone.]
1. The column of bones in the back which sustains and gives firmness to the frame; the spine; the vertebral or spinal column.
2. Anything like, or serving the purpose of, a backbone.
The lofty mountains on the north side compose the granitic axis, or backbone of the country.
Darwin.
We have now come to the backbone of our subject.
Earle.
3. Firmness; moral principle; steadfastness.
Shelley's thought never had any backbone.
Shairp.
To the backbone, through and through; thoroughly; entirely. “Staunch to the backbone.” Lord Lytton.