"Let the cat out of the bag" means:

• Answer: To reveal a secret unintentionally.

• Let the cat out of the bag:
English meaning: to allow a secret to be known, usually without intending to.
Bangla meaning: গোপন কথা বলে ফেলা

Example:
- I was trying to keep the party a secret, but Mel went and let the cat out of the bag.

Source: Cambridge Dictionary.