To turn pale (in the face) from fear, shock, or illness; to become ashen or pallid.
幽霊の話を聞いて彼は青ざめた。
He turned pale when he heard the ghost story.
発表中に失敗して、彼女の顔が青ざめた。
She went pale after making a mistake during the presentation.
急に体調が悪くなり、青ざめて倒れた。
She suddenly felt ill, went pale, and collapsed.