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and that's flat

A British expression used to signal that a decision is final and the speaker will not entertain further argument — equivalent to 'and that's that' or 'end of discussion.' The word 'flat' here means definitive or absolute, the same sense found in 'flat refusal' or 'flat out.' Now largely dated, it was typically spoken with a dismissive, authoritative tone by someone asserting their position.

ənd ˈðæts ˈflætDocumented since 1850shistorical58 viewsLast reviewed Jun 29, 2026+ Add a definition
🇬🇧 British & Irish slang
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Born ~1850 · no dated citations yet
1850BornToday, 2026

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UK
#1·Apr 28, 2026UK

A British expression used to signal that a decision is final and the speaker will not entertain further argument — equivalent to 'and that's that' or 'end of discussion.' The word 'flat' here means definitive or absolute, the same sense found in 'flat refusal' or 'flat out.' Now largely dated, it was typically spoken with a dismissive, authoritative tone by someone asserting their position. You might still encounter it in older British fiction or from speakers of a certain generation.

You're not going to that party on a school night, and that's flat.
Origin: From the adjectival use of 'flat' in British English meaning absolute or definitive, as in 'flat denial.' Dates to at least the 19th century in colloquial British usage. Editorial expansion authored on Slangora.
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UK
#2·Apr 28, 2026UK

A dated British informal phrase used to close a discussion or declare a final decision, equivalent to and that's that. The flat element means definitive and without further discussion. Signals the speaker has made up their mind and will not be moved. Somewhat old-fashioned in register now; more commonly encountered in older British writing and speech than in contemporary use.

She told him he was staying home for Christmas and that's flat — no negotiation, no appeal.
Origin: From flat in the sense of definite or absolute; the phrase functions as a rhetorical full stop. Editorial expansion authored on Slangora (model-assisted, hedged).
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UK
#3·Apr 27, 2026UK

(UK, dated, informal) And that's that.

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🇬🇧About British & Irish slang slang

UK and Irish slang — Cockney, Scouse, Geordie, Yorkshire, Glaswegian, Brummie, Welsh, West Country, plus Irish English. Centuries of regional dialects feeding into modern British and Irish street talk.

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