someone's jaw drops (open)

US /ˈsʌm.wʌnz dʒɔː drɑps (ˈoʊ.pən)/
UK /ˈsʌm.wʌnz dʒɔː drɑps (ˈoʊ.pən)/
"someone's jaw drops (open)" picture
1.

입이 떡 벌어지다, 깜짝 놀라다

used to say that someone looks very surprised or shocked

:
When she announced her engagement, everyone's jaw dropped.
그녀가 약혼을 발표했을 때, 모두의 입이 떡 벌어졌다.
My jaw dropped open when I saw the price of the new car.
새 차 가격을 보고 입이 떡 벌어졌다.