a sharp rigid animal process or appendage; as a porcupine quill or a ridge on a bone or a ray of a fish fin
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"
a small sharp-pointed tip resembling a spike on a stem or leaf
in or to or toward the rear; "he followed behind"; "seen from behind, the house is more imposing than it is from the front"; "the final runners were far behind"
remaining in a place or condition that has been left or departed from; "when he died he left much unfinished work behind"; "left a large family behind"; "the children left their books behind"; "he took off with a squeal of tires and left the other cars far behind"
in debt; "he fell behind with his mortgage payments"; "a month behind in the rent"; "a company that has been run behindhand for years"; "in arrears with their utility bills"
in or into an inferior position; "fell behind in his studies"; "their business was lagging behind in the competition for customers"
of timepieces; "the clock is almost an hour slow"; "my watch is running behind"