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drumming (noise); beating; pounding; banging; booming; stamping
rapidly; quickly; steadily
continuously; one after the other; in succession
雨がどんどん強くなってきた。
The rain kept getting heavier.
どんどん進んでください。
Please proceed quickly.
遠慮しないでどんどん質問してね。
Don't hesitate — ask questions freely.