Meaning : The series of vertebrae forming the axis of the skeleton and protecting the spinal cord.
Example :
The fall broke his back.
Synonyms : back, rachis, spinal column, spine, vertebral column
Meaning : 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.
Example :
The title and author were printed on the spine of the book.
Synonyms : spine
Meaning : The part of a network that connects other networks together.
Example :
The backbone is the part of a communication network that carries the heaviest traffic.