🎆 首先是（用力地）投入，跳进，比如跳到泳池里🏊：
The pool was declared open and eager swimmers plunged in.
游泳池刚刚宣布开门，游泳的人就急切地跳入池中。
🎆 还有这里经济学人用到的plunge into talks（开始会谈）。
plunge into：to start doing sth in an enthusiastic way, especially without thinking carefully about what you are doing 热情投入；贸然行动
She was about to plunge into her story when the phone rang.
她刚要开始大谈她的经历，电话响了。
🎆 被动用法：使经历，使陷入（不快的事情）
以前小的时候，只要雷雨天就知道，马上要停电啦。就跟每个星期二电视就停台一样。（暴露年龄）
There was a flash of lightning and the house was plunged into darkness.
雷电闪过，房子陷入一片黑暗之中。
