shoot your mouth off
US /ʃuːt jʊər maʊθ ɔːf/
UK /ʃuːt jʊər maʊθ ɔːf/

1.
입이 가볍다, 입방정 떨다
to talk too much, especially in a boastful or indiscreet way
:
•
He tends to shoot his mouth off after a few drinks.
그는 술 몇 잔 마시면 입이 가벼워지는 경향이 있어.
•
Don't shoot your mouth off about the surprise party.
깜짝 파티에 대해 입방정 떨지 마.