your jaw drops

(one's) jaw drops

One shows utter shock or great surprise, especially upon learning unexpected news. Our jaws dropped when we found out how much they were paying in rent. Oh my gosh, I can't believe you're going to have a baby! My jaw is dropping!
See also: drop, jaw

your ˈjaw drops

your mouth opens because you are very surprised: When they told her that she had won a million dollars, her jaw dropped in amazement. ▶ ˈjaw-dropping adj.: Taking the desert road was a jaw-dropping experience.
See also: drop, jaw