(1):

(n.) That which is behind, and forms the back of, anything, usually giving strength or stability.

(2):

(p. pr. & vb. n.) of Back

(3):

(n.) Support or aid given to a person or cause.

(4):

(n.) The preparation of the back of a book with glue, etc., before putting on the cover.

(5):

(n.) The act of moving backward, or of putting or moving anything backward.