In human beings, the hinder part of the body, extending from the neck to the end of the spine; in other animals, that part of the body which corresponds most nearly to such part of a human being; as, the back of a horse, fish, or lobster. An extended upper part, as of a mountain or ridge. [The mountains] their broad bare backs upheave Into the clouds. Milton. The outward or upper part of a thing, as opposed to the inner or lower part; as, the back of the hand, the back of the foot, the back of a hand rail. Methought Love pitying me, when he saw this, Gave me your hands, the backs and palms to kiss. Donne. The part opposed to the front; the hinder or rear part of a thing; as, the back of a book; the back of an army; the back of a chimney. The part opposite to, or most remote from, that which fronts the speaker or actor; or the part out of sight, or not generally seen; as, the back of an island, of a hill, or of a village. The part of a cutting tool on the opposite side from its edge; as, the back of a knife, or of a saw. A support or resource in reserve. This project Should have a back or second, that might hold, If this should blast in proof. Shak. The keel and keelson of a ship. The upper part of a lode, or the roof of a horizontal underground passage. A garment for the back; hence, clothing. A bak to walken inne by daylight. Chaucer. Behind one's back, when one is absent; without one's knowledge; as, to ridicule a person behind his back. -- Full back, Half back, Quarter back (Football), players stationed behind those in the front line. -- To be or lie on one's back, to be helpless. -- To put, or get, one's back up, to assume an attitude of obstinate resistance (from the action of a cat when attacked.). [Colloq.] -- To see the back of, to get rid of. -- To turn the back, to go away; to flee. -- To turn the back on one, to forsake or neglect him.