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.

la mâchoire tombe, être stupéfait

used to say that someone looks very surprised or shocked

:
When she announced her engagement, everyone's jaw dropped.
Quand elle a annoncé ses fiançailles, la mâchoire de tout le monde est tombée.
My jaw dropped open when I saw the price of the new car.
Ma mâchoire est tombée quand j'ai vu le prix de la nouvelle voiture.