1To jump or dive into (e.g., water) with force; figuratively, to plunge into a new situation or start something boldly.
子どもがプールに飛び込んだ。
The child jumped into the pool.
彼は思い切って新しい仕事に飛び込んだ。
He took the plunge and started a new job.
危ないから、橋から飛び込まないでください。
It's dangerous, so please don't jump off the bridge.
助けるために彼は川に飛び込んだ。
He jumped into the river to help.
2To burst into or barge into a room or place; to enter suddenly and forcefully (often implies intrusion).
彼が慌てて部屋に飛び込んできた。
He rushed and burst into the room.
許可なく会議室に飛び込むのは失礼だ。
It's rude to barge into the conference room without permission.
泥棒が店に飛び込んできて、品物を奪って逃げた。
A thief burst into the shop, grabbed items, and ran away.