[ bak ]
See synonyms for: backbackedbacking on

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

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

  1. the rear portion of any part of the body: the back of the head.

  2. the whole body, with reference to clothing: the clothes on his back.

  3. ability for labor; effort or strength: He put his back into the task.

  4. the part opposite to or farthest from the front; the rear part: the back of a hall.

  5. the part that forms the rear of any object or structure: the back of a chair.

  6. the area directly behind a person: Face the town with the river at your back and follow the main street up the hill.

  7. the part that covers the back: the back of a jacket.

  8. the spine or backbone: The fall broke his back.

  9. any rear part of an object serving to support, protect, etc.: the back of a binder.

  10. Nautical, Aeronautics. the forward side of a propeller blade (opposed to face, def. 22).

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

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

  13. the backs, grounds along the River Cam in back of certain colleges at Cambridge University in England: noted for their great beauty.

  14. Architecture. extrados.

  15. Carpentry.

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

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

  16. Mining. the roof of a stope or drift.

  17. 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.

verb (used with object)
  1. to support, as with authority, influence, help, or money (often followed by up): to back a candidate;to back up a theory with facts.

  2. to bet on: to back a horse in the race.

  1. to cause to move backward (often followed by up): to back a car.

  2. to furnish with a back: to back a book.

  3. to lie at the back of; form a back or background for: a beach backed by hills.

  4. to provide with an accompaniment: a singer backed by piano and bass.

  5. to get upon the back of; mount.

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

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

  8. 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.

verb (used without object)
  1. to go or move backward (often followed by up).

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

  1. situated at or in the rear: at the back door;back fence.

  2. far away or removed from the front or main area, position, or rank; remote: back settlements.

  1. belonging to the past: back files;back issues.

  2. in arrears; overdue: back pay.

  3. coming or going back; moving backward: back current.

  4. Navigation. reciprocal (def. 7).

  5. 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.

Verb Phrases
  1. back away, to retreat; withdraw: They gradually began to back away from their earlier opinion.

  2. 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.

  1. 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.

  2. back 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.

  3. 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.

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

Idioms about back

  1. 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.

  2. back and forth, South Midland U.S.

    • to go back and forth, as in running errands or visiting: He spent the day back and forthing to the post office.

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

  1. 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.

  2. 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.

  3. 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.

  4. break someone's back, to cause a person to fail, especially to cause to become bankrupt: His family's extravagance is breaking his back.

  5. 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.

  6. 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.

  7. get one's back up, Informal. to become annoyed; take offense: She gets her back up whenever someone mentions her family's influence.

  8. get / have someone’s back, Informal. to help and protect someone if necessary, especially in a time of trouble: If he needs anything, I hope he knows I’ve got his back.: Also have got someone's back .

  9. have one's back to the wall, to be in a difficult or hopeless situation.

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

  11. on someone's back, Informal. finding fault with or disturbing someone: The boss is always on my back about promptness.

  12. pat on the back. pat1 (defs. 9, 11).

  13. a stab in the back. stab (def. 12).

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

  15. 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.

  16. watch one’s back, Slang. to be on guard: Your assistant is gunning for your job—watch your back!

Origin of back

First recorded before 1000; Middle English bak, Old English bæc “back of the body”; cognate with Old Frisian bek, Old Saxon, Old Norse bak; perhaps from Indo-European bhogo- (unattested) “bending”; cf. bacon

synonym study For back

32. Back, hind, posterior, rear refer to something situated behind something else. Back means the opposite of front: back window. Hind, and the more formal word posterior, suggest the rearmost of two or more often similar objects: hind legs; posterior lobe. Rear is used of buildings, conveyances, etc., and in military language it is the opposite of fore: rear end of a truck; rear echelon.

usage note For back

56. Although some object to their use, the phrases in back of and the shorter—and much older— back of with the meaning “behind” are fully established as standard in American English: The car was parked ( in ) back of the house. Both phrases occur in all types of speech and writing.

Other words for back

Opposites for back

Other words from back

  • back·less, adjective

Words that may be confused with back

Words Nearby back

Other definitions for back (2 of 3)

[ bak ]

  1. at, to, or toward the rear; backward: to step back.

  2. in or toward the past: to look back on one's youth; They met in Chicago back in 1976.

  1. at or toward the original starting point, place, or condition: to go back to the old neighborhood.

  2. in direct payment or return: to pay back a loan; to answer back.

  3. in a state of restraint or retention: to hold back the tears; to hold back salary.

  4. in a reclining position: to lean back; to lie back.

Verb Phrases
  1. go back on,

    • to be treacherous or faithless to; betray: to go back on friends.

    • to fail to keep; renege on: to go back on promises.

Origin of back

First recorded in 1480–90; shortening of aback

Other definitions for back (3 of 3)

[ bak ]

  1. a large tub, vat, or cistern used by dyers, brewers, distillers, etc., to hold liquids.

  2. a broad-beamed ferryboat hauled across a body of water by a rope or chain.

Origin of back

First recorded in 1685–95; from Dutch bak “tub, trough,” from Late Latin bacca “water container”; compare French bac “ferryboat, punt”; see basin Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use back in a sentence

British Dictionary definitions for back (1 of 2)


/ (bæk) /

  1. the posterior part of the human body, extending from the neck to the pelvis: Related adjective: dorsal

  2. the corresponding or upper part of an animal

  1. the spinal column

  2. the part or side of an object opposite the front

  3. the part or side of anything less often seen or used: the back of a carpet; the back of a knife

  4. the part or side of anything that is furthest from the front or from a spectator: the back of the stage

  5. the convex part of something: the back of a hill; the back of a ship

  6. something that supports, covers, or strengthens the rear of an object

  7. ball games

    • a mainly defensive player behind a forward

    • the position of such a player

  8. the part of a book to which the pages are glued or that joins the covers

  9. mining

    • the side of a passage or layer nearest the surface

    • the earth between that level and the next

  10. the upper surface of a joist, rafter, slate, tile, etc, when in position: Compare bed (def. 13)

  11. at one's back behind, esp in support or pursuit

  12. at the back of one's mind not in one's conscious thoughts

  13. behind one's back without one's knowledge; secretly or deceitfully

  14. break one's back to overwork or work very hard

  15. break the back of to complete the greatest or hardest part of (a task)

  16. on one's back or flat on one's back incapacitated, esp through illness

  17. get off someone's back informal to stop criticizing or pestering someone

  18. have on one's back to be burdened with

  19. on someone's back informal criticizing or pestering someone

  20. put one's back into to devote all one's strength to (a task)

  21. put someone's back up or get someone's back up to annoy someone

  22. see the back of to be rid of

  23. back of beyond

    • the back of beyond a very remote place

    • Australian in such a place (esp in the phrase out back of beyond)

  24. turn one's back on

    • to turn away from in anger or contempt

    • to refuse to help; abandon

  25. with one's back to the wall in a difficult or desperate situation

verb(mainly tr)
  1. (also intr) to move or cause to move backwards

  2. to provide support, money, or encouragement for (a person, enterprise, etc)

  1. to bet on the success of: to back a horse

  2. to provide with a back, backing, or lining

  3. to provide with a music accompaniment: a soloist backed by an orchestra

  4. to provide a background for; be at the back of: mountains back the town

  5. to countersign or endorse

  6. archaic to mount the back of

  7. (intr; foll by on or onto) to have the back facing (towards): the house backs onto a river

  8. (intr) (of the wind) to change direction in an anticlockwise direction in the northern hemisphere and a clockwise direction in the southern: See veer 1 (def. 3a)

  9. nautical to position (a sail) so that the wind presses on its opposite side

  10. back and fill

    • nautical to manoeuvre the sails by alternately filling and emptying them of wind to navigate in a narrow place

    • to vacillate in one's opinion

  1. situated behind: a back lane

  2. of the past: back issues of a magazine

  1. owing from an earlier date: back rent

  2. mainly US, Australian and NZ remote: back country

  3. (of a road) not direct

  4. moving in a backward direction: back current

  5. phonetics of, relating to, or denoting a vowel articulated with the tongue retracted towards the soft palate, as for the vowels in English hard, fall, hot, full, fool

  1. at, to, or towards the rear; away from something considered to be the front; backwards; behind

  2. in, to, or towards the original starting point, place, or condition: to go back home; put the book back; my headache has come back

  1. in or into the past: to look back on one's childhood

  2. in reply, repayment, or retaliation: to hit someone back; pay back a debt; to answer back

  3. in check: the dam holds back the water

  4. in concealment; in reserve: to keep something back; to hold back information

  5. back and forth to and fro

  6. back to front

    • in reverse

    • in disorder

Origin of back

Old English bæc; related to Old Norse bak, Old Frisian bek, Old High German bah
  • See also back down, back off, back out, back up

British Dictionary definitions for back (2 of 2)


/ (bæk) /

  1. a large tub or vat, esp one used by brewers

Origin of back

C17: from Dutch bak tub, cistern, from Old French bac, from Vulgar Latin bacca (unattested) vessel for liquids

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Idioms and Phrases with back


In addition to the idioms beginning with back

  • back against the wall
  • back alley
  • back and fill
  • back and forth
  • back away
  • back burner, on a
  • back door
  • back down
  • back in circulation
  • back in harness
  • back number
  • back of
  • back of beyond
  • back off
  • back of one's hand
  • back of one's mind
  • back on one's feet
  • back order
  • back out
  • back street
  • back the wrong horse
  • back to back
  • back to basics
  • back to the drawing board
  • back to the salt mines
  • back to the wall
  • back up
  • back water

also see:

  • a while back
  • behind someone's back
  • break one's back
  • break the back of
  • call back
  • choke back
  • come back
  • cut back
  • double back
  • draw back
  • drop back
  • eyes in the back of one's head
  • fall back
  • fall back on
  • fall over (backward)
  • flat on one's back
  • from way back
  • get back
  • get one's back up
  • give the shirt off one's back
  • go back on one's word
  • hang back
  • hark(en) back
  • hold back
  • in one's own backyard
  • kick back
  • knock back
  • know like a book (the back of one's hand)
  • left-handed (back-handed) compliment
  • like water off a duck's back
  • look back
  • monkey on one's back
  • off someone's back
  • pat on the back
  • pay back in someone's own coin
  • pin someone's ears back
  • play back
  • plow back
  • pull back
  • put one's back in it
  • put one's back up
  • roll back
  • scratch someone's back
  • see the back of
  • set back
  • set back on one's heels
  • set one back
  • set the clock back
  • sit back
  • slap on the back
  • snap back
  • stab in the back
  • take aback
  • take a back seat
  • take back
  • talk back
  • think back
  • throw back
  • turn back
  • turn one's back on
  • when someone's back is turned
  • with one arm tied behind one's back
  • you scratch my back and I'll scratch yours

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.