Not reveal a secret, esp of dishonest or criminal activity
They tried to buy his silence, ie to pay him not to reveal a secret.
reveal a secret;betray sb
Now Alexander is going to reveal a secret of how to cook a sandwich from McDonald's.
(cause sb to)make a mistake,reveal a secret,etc
Although the severe torture of the enemy left Jiang Jie unkempt and scarred, she still did not reveal a secret of the Party.
Therefore, 'let the cat out of the bag' must mean something like 'reveal a secret' or 'tell a secret'.
I want to speak truth through this letter and open my heart and reveal a secret to you.
