Meaning : The series of vertebrae forming the axis of the skeleton and protecting the spinal cord.
Example :
The fall broke his back.
Synonyms : back, backbone, rachis, spinal column, 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 : backbone
Meaning : A sharp rigid animal process or appendage. As a porcupine quill or a ridge on a bone or a ray of a fish fin.