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to stay indoors; to be confined indoors
彼は部屋に引き籠もった。
He shut himself in his room.
体調が悪くて一日中引き籠もっている。
Not feeling well, he stayed indoors all day.
問題を一人で抱えて引き籠もるのは危険だ。
Shutting yourself away while carrying problems alone is dangerous.