Backbone

Part of speech: noun (n.)

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.