1. （尤指向水中）纵身投入，一头进入
    If something or someone plunges in a particular direction, especially into water, they fall, rush, or throw themselves in that direction.

    e.g. At least 50 people died when a bus plunged into a river...
           一辆公共汽车栽进河里，造成至少50人丧生。
    e.g. He ran down the steps to the pool terrace and plunged in.
           他跑下台阶来到泳池露台，纵身跳进池里。

2. 将…投入；将…插入；将…刺进
    If you plunge an object into something, you push it quickly or violently into it.

    e.g. A soldier plunged a bayonet into his body...
           一名士兵将刺刀插进了他的身体。
    e.g. She plunged her face into a bowl of cold water...
           她把脸扎进一盆凉水里。

3. （使）突然陷入；（使）突然遭受
    If a person or thing is plunged into a particular state or situation, or if they plunge into it, they are suddenly in that state or situation.

    e.g. The government's political and economic reforms threaten to plunge the country into chaos...
           政府的政治和经济改革可能会使国家陷入混乱局面。
    e.g. 8,000 homes were plunged into darkness as electricity cables crashed down...
           由于电缆损毁，8,000户家庭顿时落入一片黑暗之中。

4. （使）投身；（使）突然开始从事
    If you plunge into an activity or are plunged into it, you suddenly get very involved in it.

    e.g. The two men plunged into discussion...
           两位男士立即投入到讨论中。
    e.g. The prince should be plunged into work...
           王子应该积极参与工作。

5. 骤降；猛跌
    If an amount or rate plunges, it decreases quickly and suddenly.

    e.g. His weight began to plunge...
           他的体重开始锐减。
    e.g. The Pound plunged to a new low on the foreign exchange markets yesterday...
           昨天在外汇市场上英镑骤跌至新低。

6. see also: plunging

7. 决定冒险尝试；采取断然行动
    If you take the plunge, you decide to do something that you consider difficult or risky.

    e.g. If you have been thinking about buying shares, now could be the time to take the plunge.
           如果你一直在考虑购买股票，现在或许是采取行动的最好时机。