backbone in WordNet English dictionary

1. a central cohesive source of support and stability
   "faith is his anchor"; "the keystone of campaign reform was the ban on soft money"; "he is the linchpin of this firm"
   anchor  mainstay  keystone  backbone  linchpin  lynchpin 
   
2. the series of vertebrae forming the axis of the skeleton and protecting the spinal cord
   "the fall broke his back"
   spinal column  vertebral column  spine  backbone  back  rachis 
   
3. the part of a network that connects other networks together
   "the backbone is the part of a communication network that carries the heaviest traffic"
   backbone 
   
4. the part of a book's cover that encloses the inner side of the book's pages and that faces outward when the book is shelved
   "the title and author were printed on the spine of the book"
   spine  backbone 
   
5. fortitude and determination
   "he didn't have the guts to try it"
   backbone  grit  guts  moxie  sand  gumption