let the cat out of the bag

US /lɛt ðə kæt aʊt əv ðə bæɡ/
UK /lɛt ðə kæt aʊt əv ðə bæɡ/
"let the cat out of the bag" picture
1.

洩露秘密, 說漏嘴

to reveal a secret, often accidentally

:
We were planning a surprise party for him, but his sister let the cat out of the bag.
我們正在為他策劃一個驚喜派對,但他妹妹洩露了秘密
I accidentally let the cat out of the bag about their engagement.
我不小心洩露了他們訂婚的秘密。