1
to pollute;to contaminate;to soil;to make dirty;to stain
その本を汚さないように扱ってくれるなら、貸してあげるよ。
You may borrow this book as long as you keep it clean.
2
to disgrace;to dishonour;to dishonor;to defile
esp. けがす
あんな行動は彼の体面を汚すものだ。
Such behavior is beneath his dignity.
Other forms
穢す 【よごす】