污垢

zhǐ jia fèng li róng yì cún liú wū gòu

指甲缝里容易存留污垢。

Dirt gets trapped easily around one's fingernails.

sī xiǎng wū gòu

思想污垢

impure thoughts

chú qù wū gòu

除去污垢

remove dirt

yī céng wū gòu

一层污垢

a layer of dirt