let slip

listen to the pronunciation of let slip
Английский Язык - Английский Язык
To divulge a secret, as by accident or mistake

He finally let slip that they plan to take over the business.

mutter, say; miss, make an error
let slip the dogs of war
begin a hostile action, start making an act of war or aggression
let slip through the fingers
miss an opportunity; lose because of recklessness
let something slip
To accidentally reveal a secret