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

Britain is flat-out refusing to be drawn into the war. —Sam McNeil, Fortune, 19 Mar. 2026

Britain is flat-out refusing to be drawn into the war. —John Leicester, Los Angeles Times, 18 Mar. 2026

Adverb

Pitchers will likely be encouraged — if not flat out directed — to leave their decision to challenge up to the catchers sitting directly on top of the strike zone. —Jeff Sanders, San Diego Union-Tribune, 18 Mar. 2026

Not everyone could play flat out. —Literary Hub, 16 Mar. 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