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flat-out

[ flat-out ]
/ ˈflætˈaʊt /
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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.
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Origin of flat-out

First recorded in 1925–30
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use flat-out in a sentence

Other Idioms and Phrases with flat-out

flat out

1

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

2

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

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