1 [C] [usu.pl] a substance that is present in small amounts in another substance, making it dirty or of poor quality 杂质: People are being advised to boil their water because certain impurities have been found in it. 水里发现了一些杂质，当局建议大家把水煮开。

2 [U] (old-fashioned 旧) the state of being morally bad 淫秽 ☞Look at purity. 参看purity。