Nearby words

  1. bacillus calmette-guérin,
  2. bacillus cereus,
  3. bacillus sphaericus,
  4. bacillus thuringiensis,
  5. bacitracin,
  6. back against the wall,
  7. back alley,
  8. back anchor,
  9. back and fill,
  10. back and forth


Origin of back

before 1000; Middle English bak, Old English bæc back of the body; cognate with Old Frisian bek, Old Saxon, Old Norse bak; perhaps < Indo-European *bhogo- bending; cf. bacon

1, 31. front.

Related formsback·less, adjective

Can be confusedback up backup

Synonym study

31. 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

55. 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. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for be flat on one's back




the posterior part of the human body, extending from the neck to the pelvisRelated adjective: dorsal
the corresponding or upper part of an animal
the spinal column
the part or side of an object opposite the front
the part or side of anything less often seen or usedthe back of a carpet; the back of a knife
the part or side of anything that is furthest from the front or from a spectatorthe back of the stage
the convex part of somethingthe back of a hill; the back of a ship
something that supports, covers, or strengthens the rear of an object
ball games
  1. a mainly defensive player behind a forward
  2. the position of such a player
the part of a book to which the pages are glued or that joins the covers
  1. the side of a passage or layer nearest the surface
  2. the earth between that level and the next
the upper surface of a joist, rafter, slate, tile, etc, when in positionCompare bed (def. 13)
at one's back behind, esp in support or pursuit
at the back of one's mind not in one's conscious thoughts
behind one's back without one's knowledge; secretly or deceitfully
break one's back to overwork or work very hard
break the back of to complete the greatest or hardest part of (a task)
on one's back or flat on one's back incapacitated, esp through illness
get off someone's back informal to stop criticizing or pestering someone
have on one's back to be burdened with
on someone's back informal criticizing or pestering someone
put one's back into to devote all one's strength to (a task)
put someone's back up or get someone's back up to annoy someone
see the back of to be rid of
back of beyond
  1. the back of beyonda very remote place
  2. Australianin such a place (esp in the phrase out back of beyond)
turn one's back on
  1. to turn away from in anger or contempt
  2. to refuse to help; abandon
with one's back to the wall in a difficult or desperate situation

verb (mainly tr)

(also intr) to move or cause to move backwards
to provide support, money, or encouragement for (a person, enterprise, etc)
to bet on the success ofto back a horse
to provide with a back, backing, or lining
to provide with a music accompanimenta soloist backed by an orchestra
to provide a background for; be at the back ofmountains back the town
to countersign or endorse
archaic to mount the back of
(intr; foll by on or onto) to have the back facing (towards)the house backs onto a river
(intr) (of the wind) to change direction in an anticlockwise direction in the northern hemisphere and a clockwise direction in the southernSee veer 1 (def. 3a)
nautical to position (a sail) so that the wind presses on its opposite side
back and fill
  1. nauticalto manoeuvre the sails by alternately filling and emptying them of wind to navigate in a narrow place
  2. to vacillate in one's opinion

adjective (prenominal)

situated behinda back lane
of the pastback issues of a magazine
owing from an earlier dateback rent
mainly US, Australian and NZ remoteback country
(of a road) not direct
moving in a backward directionback current
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


at, to, or towards the rear; away from something considered to be the front; backwards; behind
in, to, or towards the original starting point, place, or conditionto go back home; put the book back; my headache has come back
in or into the pastto look back on one's childhood
in reply, repayment, or retaliationto hit someone back; pay back a debt; to answer back
in checkthe dam holds back the water
in concealment; in reserveto keep something back; to hold back information
back and forth to and fro
back to front
  1. in reverse
  2. in disorder

Word Origin for back

Old English bæc; related to Old Norse bak, Old Frisian bek, Old High German bah




a large tub or vat, esp one used by brewers

Word Origin for 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

Word Origin and History for be flat on one's back
Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for be flat on one's back




The posterior portion of the trunk of the human body between the neck and the pelvis; the dorsum.
The backbone or spine.

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Idioms and Phrases with be flat on one's 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.