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

There is almost unanimous agreement that the challenge of a flat-out qualifying lap has diminished as a consequence of the demand for energy management.

From BBC • Apr. 3, 2026

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

From Salon • Mar. 11, 2026

At that awards show, when former Times columnist Amy Kaufman — then recently engaged herself — asked the “Dune” actor flat-out if she was engaged, Zendaya flashed her ring, smiled coyly and shrugged her shoulders.

From Los Angeles Times • Mar. 2, 2026

But buyers with FHA loans sometimes face flat-out rejection, and some sellers state upfront that they won’t do business with FHA buyers.

From MarketWatch • Dec. 12, 2025

We’d always wondered what would happen if we flat-out disobeyed him.

From "The Poisonwood Bible" by Barbara Kingsolver