At maximum speed or effort; or to be completely exhausted; or to do something directly and plainly.
Going as fast or working as hard as you possibly can, or being so tired you can barely move.
3 meanings, ordered from most common to least. Color-coded by CEFR level.
At maximum speed or with total effort.
"We were working flat out all weekend to finish the project on time."
We've been going flat out since January.
— Common idiomatic usage in British journalism; cited widely in The Guardian and BBC news reports.
Completely exhausted; unable to do anything more.
"After the marathon, she was flat out on the sofa for the rest of the day."
Directly and without hesitation; plainly (used as an adverb).
"He flat out refused to apologize for what he had said."
He flat out lied to Congress.
— Common political commentary phrase; widely used in US news media during congressional hearings.
Lying flat with all air out — suggesting complete exhaustion or maximum effort with no reserve.
Going as fast or working as hard as you possibly can, or being so tired you can barely move.
Used widely in British and American English. As an adverb ('flat out lying'), it means completely or plainly. As an adjective ('I'm flat out'), it means exhausted or very busy. Tone is energetic or emphatic.
Natural word combinations native speakers use most often.
The five tense forms you'll use most often.
Listen to native speakers using "flat out" in real YouTube videos — click a clip to watch it on Looplines.
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