Back (băk), n. [AS. bæc, bac; akin to Icel., Sw., & LG. bak, Dan. bag; cf. OHG. bahho ham, Skr. bhaj to turn, OSlav. bēgŭ flight. Cf. Bacon.] 1. 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.
2. An extended upper part, as of a mountain or ridge.
their broad bare backs upheave
Into the clouds.
Milton.
3. 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.
4. 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.
5. 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.
6. The part of a cutting tool on the opposite side from its edge; as, the back of a knife, or of a saw.
7. A support or resource in reserve.
This project
Should have a back or second, that might hold,
If this should blast in proof.
Shak.
8. (Naut.) The keel and keelson of a ship.
9. (Mining) The upper part of a lode, or the roof of a horizontal underground passage.
10. 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, orget, one's back up, to assume an attitude of obstinate resistance (from the action of a cat when attacked). — 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.