1the series of vertebrae extending from the skull to the pelvis; the spine:prickles of sweat broke out along her backbone figurativethe great Pennine range is the backbone of England
US the spine of a book.
Biochemistry the main chain of a polymeric molecule.
2the chief support of a system or organization:these firms are the backbone of our industrial sector
[mass noun] strength of character:he has enough backbone to see us through this difficulty
3 Computing & Telecommunications a high-speed, high-capacity digital connection which forms the axis of a local or wide area network.