scum
noun uk/skʌm/ us/skʌm/
(DIRT)
[ U ]（液体上的）浮沫，浮渣，浮垢
a layer of unpleasant or unwanted material that has formed on the top of a liquid
The lake near the factory was covered with grey, foul-smelling scum. 这家工厂附近的湖面上浮着一层灰蒙蒙、散发着臭气的浮垢。
(IMMORAL PERSON)
[ C or U ] informal plural scum人渣；败类
a very bad or immoral person or group of people
People who organize dog fights are scum in my opinion! 我认为那些组织斗狗的人是人渣！
His boss treats him like scum (= very badly). 他老板不把他当人看。
racist scum 种族主义暴徒
Idiom
the scum of the earthidiom informal 人渣，最恶劣的人
the worst type of people that can be imagined
These men are the scum of the earth. 这些人都是人渣。