Английский словарь американских идиом - let the cat out of the bag

{v. phr.}, {informal} To tell about something that is supposed to be a secret. * /We wanted to surprise Mary with a birthday gift, but Allen let the cat out of the bag by asking her what she would like./ - Sometimes used in another form. * /Well, the cat is out of the bag - everybody knows about their marriage./ Compare: GIVE AWAY(3), LET OUT(2), SPILL THE BEANS.