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to be surprised; to be taken aback; to be amazed; to be astonished; to be shocked
to be frightened; to be startled; to be alarmed
彼の変わりように誰もが駭く。
Everyone is astonished at how much he has changed.
大きな音に駭いて振り返った。
I was startled by a loud noise and turned around.
突然の大きな音に駭いた。
I was startled by a sudden loud noise.