From Longman Dictionary of Contemporary Englishbackboneback‧bone /ˈbækbəʊn $ -boʊn/ ●○○ noun 1 
[countable]HBAHBH the row of connected bones that go down the middle of your back SYN spine2 → the backbone of something3 [uncountable]GOOD/MORAL courage and determination Stuart doesn’t have the backbone to be a good manager.
[countable]HBAHBH the row of connected bones that go down the middle of your back SYN spine2 → the backbone of something3 [uncountable]GOOD/MORAL courage and determination Stuart doesn’t have the backbone to be a good manager.Examples from the Corpus
backbone• This, at least, is some suggestion of a backbone, but the larva does not keep it for very long.• But they and other progressives had both the brass and backbone to make themselves heard.• This effectively creates a limited number of entry points into the backbone and simplifies network management. 