let the cat out of the bag
US /lɛt ðə kæt aʊt əv ðə bæɡ/
UK /lɛt ðə kæt aʊt əv ðə bæɡ/
1.
to reveal a secret, often accidentally
:
•
We were planning a surprise party for him, but his sister let the cat out of the bag.
•
I accidentally let the cat out of the bag about their engagement.