flat-out

1 of 2

adjective

ˈflat-ˌau̇t 

1

: being or going at maximum effort or speed

2

: out-and-out, downright

It was a flat-out lie.

flat out

2 of 2

adverb

1

: in a blunt and direct manner : openly

… called flat out for revolution.

—National Review

2

: at top speed or peak performance

the car does 180 m.p.h. flat out

3

usually flat-out

ˈflat-ˌau̇t 

: absolutely, downright

—usually used as an intensive

is just flat-out confusing

Synonyms of flat-out

Adjective

• utter
• sheer
• absolute
• unconditional
• outright
• complete
• pure
• simple
• total
• definite
• damned
• damn
• downright
• perfect
• very

Examples of flat-out in a Sentence

Adjective

regarded their son-in-law as a flat-out loser and let him know it

Adverb

I told him flat out that I have no intention of marrying him.

We asked for more time but they refused us flat out.

The car does 180 mph flat out.

Recent Examples on the Web

Adjective

Only the latter seemed flat-out opposed to the scheme, though. — James Horncastle, New York Times, 30 July 2026

The letter promised an additional $20 million in funds for countries that accept, which sound something like bribery, dare say flat-out payment for a yes vote. — Miami Herald, 30 July 2026

Adverb

Christian flat out tells Bryan to do anything else because the gown is so boring, but Bryan could not be more disinterested in his advice. — Roxana Hadadi, Vulture, 31 July 2026

Certain iconic corners are no longer taken flat out, and the need to recharge batteries has led to people calling the racing artificial. — Matt Reigle Outkick, FOXNews.com, 30 July 2026

Word History

First Known Use

Adjective

1906, in the meaning defined at sense 1

Adverb

1932, in the meaning defined at sense 1

Rhymes for flat-out

• about
• bailout
• blackout
• blowout
• breakout
• burnout
• buyout
• checkout
• closeout
• cutout
• devout
• dropout