If you plunge an object into something, you push it quickly or violently into it.
(猛地) 将…推入
Plunge is also a noun.
投入 (水中); 俯冲 • ...a plunge into cold water. …向着冰冷的水中的纵身一跳。
His sudden plunge into the field of international diplomacy is a major surprise.
他突然进入了国际外交领域,让人十分意外。