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

There are also rule tweaks starting in Miami to address the biggest criticisms of the new regulations, designed to make qualifying a flat-out dash (rather than a strategic game of energy use and slowing down on straights) and limit dangerous speed swings in races. —Sahil Kapur, NBC news, 30 Apr. 2026

LivaNova’s suggestion that the bacteria could have come from the water at The University of Kansas Hospital, Johnson said, was flat-out wrong. —Judy L. Thomas, Kansas City Star, 29 Apr. 2026

Adverb

Gabriel Martinelli was lying flat out. —Amy Lawrence, New York Times, 26 Apr. 2026

The other kids must have found its inhabitants repulsive or boring, but I was drawn to a cobra that was lying flat out and minding its own business. —John McPhee, New Yorker, 20 Apr. 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