Webster's Revised Unabridged Dictionary · 1913

Backbone

Backbone (bak"bōn`) , noun

[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
Collocations (1)
To the backbone , through and through; thoroughly; entirely. Staunch to the backbone. — Lord Lytton