noun
plural spines
[count] :the row of connected bones down the middle of the back :backbone
[count] :a sharp, pointed part on an animal or plant
[noncount] informal :courage or strength of character
[count] :the part of a book to which the pages are attached
A book's spine often has the title and author's name printed on it.
up/down your spine
If something sends a chill/shiver up/down your spine or if a chill/shiver runs up/down your spine, you become frightened, thrilled, etc.
US