noun · An enclosure in a canal or river with gates at each end, used for raising or lowering boats between different water levels.

这艘货轮正在通过三峡大坝的五级水闸。

noun · A movable gate or structure used to control the flow or level of water, such as a floodgate or water gate.

由于降雨量过大，管理人员决定开启水闸泄洪。