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

They require energy management around the lap, have been criticised for preventing drivers going flat-out in qualifying.

From BBC • Apr. 23, 2026

I study music every night, and I have the privilege of calling someone like Babyface and just flat-out asking him, “How did you write ‘Whip Appeal’?”

From Los Angeles Times • Mar. 26, 2026

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

From Salon • Mar. 11, 2026

So Sauer’s claim that Murphy forced an unscheduled emergency stopover in Djibouti is just flat-out false.

From Slate • Feb. 28, 2026

“Oh, no.. Creepy is like spiders and rats and, you know, things that make chills run down your spine. You’re just....difficult,” said Gregor, trying to be honest but not flat-out rude.

From "Gregor the Overlander" by Suzanne Collins