taru-adjective, adverb taking the 'to' particle
surprised; startled; with a look of surprise
Literary or classical word describing a sudden surprised expression or change in demeanor. Often used adverbially with と (e.g., 瞿然として). Rare in everyday speech.
彼はその知らせを聞いて瞿然とした。
He looked startled upon hearing the news.
瞿然として目を見開いた。
He opened his eyes wide in surprise.