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

That statement stood in stark contrast to the longstanding stodginess of the Kings, which dissipated into flat-out ineffectiveness under Jim Hiller for three quarters of last season until he was sacked. —Andrew Knoll, Daily News, 11 June 2026

And for the first time this season, the cars wrecked completely flat-out; with no long straights and plenty of braking zones, the cars were not energy-limited for once this season. —Jonathan M. Gitlin, ArsTechnica, 8 June 2026

Adverb

The Red Sox have been flat out bad. —Mac Cerullo, Boston Herald, 14 June 2026

With the 2026 cars, the drivers also get a rare chance to push flat out without many engine energy limitations. —Luke Smith, New York Times, 6 June 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