backbone

noun3

1. •
   The series of vertebrae, separated by disks, that encloses and protects the spinal cord, and runs down the middle of the back in vertebrate animals.
2. •
   (figurative) Any fundamental support, structure, or infrastructure.

   • Before automobiles, railroads were a backbone of commerce.
3. •
   (figurative) Courage, fortitude, or strength.

   • He would make a good manager, if he had a little more backbone.