What is the Meaning of the Idiom
LET THE CAT OUT OF THE BAG?

Definition:

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.)

Examples:

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.

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