let the cat out of the bag

let the cat out of the bag
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.
Categories: informal verb