1. 高原
    A plateau is a large area of high and fairly flat land.

    e.g. A broad valley opened up leading to a high, flat plateau of cultivated land.
           一条宽阔的山谷展现在眼前，通往一处平整的开垦地高原。

2. （活动或进程中的）稳定阶段，停滞时期
    If you say that an activity or process has reached a plateau, you mean that it has reached a stage where there is no further change or development.

    e.g. The US heroin market now appears to have reached a plateau...
           美国的海洛因市场现在似乎已到了停滞期。
    e.g. I think the economy is stuck on a kind of plateau of slow growth.
           我认为经济将停留在缓慢发展的阶段。

3. （活动、进程、成本等）达到稳定阶段，进入停滞时期
    If something such as an activity, process, or cost plateaus or plateaus out, it reaches a stage where there is no further change or development.

plateau的翻译

    e.g. Evelyn's career is accelerating, and mine is plateauing out a bit...
           伊夫琳的职业生涯蒸蒸日上，而我的则停滞不前。
    e.g. The shares plateaued at 153p.
           股票稳定在153便士。