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to jump in; to leap in; to plunge into; to dive
to burst in; to barge in
暑くてプールに飛びこみたくなった。
It was so hot that I wanted to jump into the pool.
猫が窓から部屋に飛びこんできた。
A cat jumped into the room through the window.
プールサイドから勢いよく飛びこんだ。
I dove energetically from the poolside.