blow the gaff
Blow the gaff is a British slang phrase meaning to reveal a secret, spill the beans, or rat someone out.
Definitions
Blow the gaff is a British slang phrase meaning to reveal a secret, spill the beans, or rat someone out. Though dated, the expression still surfaces in British crime fiction, period dramas, and from older speakers who enjoy its old-school flavour. To blow the gaff is to expose what was meant to stay hidden — whether that's a scam, a surprise, or someone's criminal activity. The 'gaff' here refers to a secret or trick, not a place.
Don't invite him along — he'll blow the gaff about the surprise party the second he has a drink in him.
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(UK, slang, obsolete) To disclose a secret.
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(UK, slang, obsolete) To inform against a person.
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- gaff68%
British / Irish slang for one's home or apartment. "Round at my gaff" = at my place. Slightly blokey register — you'd say it to mates, not your manager. Common in London, Manchester, and Dublin.
- gaff68%
An outcry; nonsense.
- gob off66%
British slang meaning to gossip, blab, or talk loudly and at length about things that aren't your business. To gob off is to let your mouth run without much filter — whether that means spilling someone else's secrets, mouthing off to an authority figure, or just filling dead air with endless chatter. 'Gob' is already British slang for mouth, so 'gobbing off' is essentially the act of letting that mouth run loose.