grey water
noun [ U ] (US usually gray water) uk/ˈɡreɪ ˌwɔː.tər/ us/ˈɡreɪ ˌwɑː.t̬ɚ/
灰水（使用过的水）
water that has been used before, for example for washing, that can be stored and used again, for example in toilets
Water companies are testing recycling units which take grey water and clean it up sufficiently for flushing toilets. 用水公司正在测试污水再利用设备，这些设备可以净化污水，其产出的净化水足以用来冲厕。