Meaning of the word "blow the gaff" in English

What does "blow the gaff" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

blow the gaff

US /bloʊ ðə ɡæf/
UK /bləʊ ðə ɡæf/

Idiom

to reveal a secret or something that was intended to be kept hidden

Example:
He almost blew the gaff about the surprise party.
Don't blow the gaff, it's supposed to be a secret.