[ flat-out ]
/ ˈflætˈaʊt /

adjective Informal.

moving or working at top speed or with maximum effort; all-out: a flat-out effort by all contestants.
downright; thoroughgoing: Many of the paintings were flat-out forgeries.

Nearby words

  1. flat-file,
  2. flat-footed,
  3. flat-grained,
  4. flat-joint pointing,
  5. flat-knit,
  6. flat-pack,
  7. flat-panel display,
  8. flat-pick,
  9. flat-plate collector,
  10. flat-rolled

Origin of flat-out

First recorded in 1925–30

Origin of flat

1275–1325; Middle English < Old Norse flatr, akin to Old English flet (see flat2), Greek platýs (see platy-, plate1

1. plane. See level. 4. low, prone. 11. outright, peremptory, categorical. 14. boring, spiritless, prosaic. 17. vapid, unsavory.

Related formsflat·ly, adverbflat·ness, nounun·flat·ted, adjective

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

British Dictionary definitions for flat out
See also flats

Derived Formsflatly, adverbflatness, noun

Word Origin for flat

C14: from Old Norse flatr; related to Old High German flaz flat, Greek platus flat, broad


/ (flæt) /


a set of rooms comprising a residence entirely on one floor of a buildingUsual US and Canadian name: apartment
British and NZ a portion of a house used as separate living quarters
NZ a house shared with people who are not members of one's own family

verb flats, flatting or flatted (intr)

Australian and NZ to live in a flat (with someone)

Word Origin for flat

Old English flett floor, hall, house; related to flat 1

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 flat out
Online Etymology Dictionary, © 2010 Douglas Harper

Idioms and Phrases with flat out

flat out


In a direct manner, bluntly. For example, He told the true story flat out. [Colloquial; mid-1900s]


At top speed, as in She was running flat out to catch the train. [Slang; c. 1930]


In addition to the idioms beginning with flat

  • flat as a pancake
  • flat broke
  • flat on one's back
  • flat out

also see:

  • caught flat-footed
  • fall flat
  • in no time (nothing flat)
  • leave flat
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.