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sudden; abrupt; unexpected; unforeseen
不意をつかれて何も言えなかった。
I was caught off guard and couldn't say anything.
彼が不意に現れたので本当に驚いた。
He appeared unexpectedly so I was really surprised.
不意の訪問にとても戸惑ってしまった。
I was very flustered by the unexpected visit.