the rear part of the human body, extending from the neck to the lower end of the spine.

the part of the body of animals corresponding to the human back.

the rear portion of any part of the body

the back of the head.

the whole body, with reference to clothing

the clothes on his back.

ability for labor; effort; endurance

He put his back into the task.

the part opposite to or farthest from the front; the rear part

the back of a hall.

the part that forms the rear of any object or structure

the back of a chair.

the part that covers the back

the back of a jacket.

the spine or backbone

The fall broke his back.

any rear part of an object serving to support, protect, etc.

the back of a binder.

Nautical, Aeronautics . the forward side of a propeller blade ( opposed to face ).

Aeronautics . the top part or upper surface of an aircraft, esp. of its fuselage.

Bookbinding . the edge of a book formed where its sections are bound together.

the backs, grounds along the River Cam in back of certain colleges at Cambridge University in England

noted for their great beauty.

Architecture . extrados.

Carpentry .

the upper side of a joist, rafter, handrail, etc.

the area of interior wall between a window stool and the floor.

Mining . the roof of a stope or drift.

Sports .

a player whose regular position is behind that of players who make initial contact with the opposing team, as behind the forward line in football or nearest the player's own goal in polo.

the position occupied by this player.

to support, as with authority, influence, help, or money (often fol. by up )

to back a candidate; to back up a theory with facts.

to bet on

to back a horse in the race.

to cause to move backward (often fol. by up )

to back a car.

to furnish with a back

to back a book.

to lie at the back of; form a back or background for

a beach backed by hills.

to provide with an accompaniment

a singer backed by piano and bass.

to get upon the back of; mount.

to write or print on the back of; endorse; countersign.

Carpentry . to attach strips of wood to the upper edge of (a joist or rafter) to bring it to a desired level.

Nautical .

to alter the position of (a sail) so that the wind will strike the forward face.

to brace (yards) in backing a sail.

to reinforce the hold of (an anchor) by means of a smaller one attached to it and dropped farther away.

to go or move backward (often fol. by up ).

Nautical . (of wind) to change direction counterclockwise ( opposed to veer ).

situated at or in the rear

at the back door; back fence.

far away or removed from the front or main area, position, or rank; remote

back settlements.

belonging to the past

back files; back issues.

in arrears; overdue

back pay.

coming or going back; moving backward

back current.

Navigation . reciprocal ( def. 7 ) .

Phonetics . (of a speech sound) produced with the tongue articulating in the back part of the mouth, as in either of the sounds of go. ?

back away, to retreat; withdraw

They gradually began to back away from their earlier opinion.

back down, to abandon an argument, opinion, or claim; withdraw; retreat

He backed down as soon as a member of the audience challenged his assertion.

back off,

to back down

Now that the time for action had arrived, it was too late to back off.

Textiles . to reverse (the spindle) in mule spinning prior to winding on the newly spun length of yarn.

back out or out of, to fail to keep an engagement or promise; withdraw from; abandon

Two entrants have backed out of competing in the marathon. You can't back out now.

back up,

to bring (a stream of traffic) to a standstill

A stalled car backed up traffic for miles.

Printing . to print a sheet again on its other side.

Printing . to fill in (the thin copper shell of an electrotype) with metal in order to strengthen it.

to move backward

Back up into the garage.

to reinforce

We backed up the cardboard with slats so it wouldn't fall down.

to support or confirm

He backed up my story and they let us go.

Computers . to duplicate (a file or a program) as a precaution against failure.

back up for, Australian Informal . to return for more of, as another helping of food. ?

back and fill

Nautical . to trim the sails of a boat so that the wind strikes them first on the forward and then on the after side.

to change one's opinion or position; vacillate.

back and forth

South Midland U.S.

to go back and forth, as in running errands or visiting

He spent the day backing and forthing to the post office.

to work in an aimless or ineffective way; expend effort with little result.

back water

Nautical . to reverse the direction of a vessel.

to retreat from a position; withdraw an opinion

I predict that the council will back water on the tax issue.

be flat on one's back

to be helpless or beaten

He's flat on his back after a long succession of failures.

to be confined to one's bed because of illness.

behind one's back

in one's absence; without one's knowledge; treacherously; secretly

I'd rather talk to him about it directly than discuss it behind his back.

break someone's back, to cause a person to fail

esp. to cause to become bankrupt

His family's extravagance is breaking his back.

break the back of

to complete the principal or hardest part of (a project, one's work, etc.)

He finally broke the back of the problem.

to overcome; defeat

They broke the back of our union.

get off one's back

Informal . to cease to find fault with or to disturb someone

The fight started when they wouldn't get off my back.

get one's back up

Informal . to become annoyed; take offense

She gets her back up whenever someone mentions her family's influence.

have one's back to the wall

to be in a difficult or hopeless situation.

in back of

behind

He hid in back of the billboard. What could be in back of his strange behavior? Also, back of.

on one's back

Informal . finding fault with or disturbing someone

The boss is always on my back about promptness.

pat on the back. pat 1 ( defs. 9

8 ) .

stab in the back. stab ( def. 13 ) .

turn one's back on

to forsake or neglect

He was unable to turn his back on any suffering creature.

to leave behind, as in anger.