flat-out

American  

[flat-out] / ˈflætˈaʊt /

adjective

Informal.

1. moving or working at top speed or with maximum effort; all-out.

   a flat-out effort by all contestants.

2. downright; thoroughgoing.

   Many of the paintings were flat-out forgeries.

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flat out Idioms  

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]

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Etymology

Origin of flat-out

First recorded in 1925–30

Example Sentences

To the extent there is no longer such a thing as a flat-out lap.

From BBC • Apr. 3, 2026

County Medical Assn. warned flat-out that smog damages human organs.

From Los Angeles Times • Mar. 26, 2026

His accusation, Jones told Salon, is flat-out false.

From Salon • Mar. 11, 2026

A 2016 consumer alert from the Federal Trade Commission, which appears to be the latest on the topic, warned people against this option, saying that the deals can be risky or “even flat-out scams.”

From MarketWatch • Feb. 4, 2026

Abnegation discourages anything done strictly for my own enjoyment, and that is what this is: my lungs burning, my muscles aching, the fierce pleasure of a flat-out sprint.

From "Divergent" by Veronica Roth