What is the Meaning of the Idiom
LET THE CAT OUT OF THE BAG?
to tell (or not keep) a secret
(Think about trying to keep a cat inside a bag! It’s a great picture for how hard it can be to keep an interesting secret.)
1. The surprise party is all planned. We are not going to tell Uncle John because he is a terrible liar, and if knows he will be sure to let the cat out of the bag.
2. They wanted to tell us in person that they were expecting a baby, but his mom let the cat out of the bag, when she asked us if we were going to come home after the baby was born.