scum
n
1 [U] layer of froth on the surface of a boiling liquid; layer of dirt on a pond or other area of still water (煮沸的液體表面的)泡沫; (池塘或其他靜止水面上的)浮垢, 浮渣.
2 [pl v] (fig derog 比喻, 貶) people considered to be bad or contemptible 一群壞人或卑賤的人: You scum! 你們這群壞蛋!
She treats smokers like the scum of the earth, ie as the worst people there are. 她把吸煙的人都當作敗類.
I wouldn't have anything to do with those scum. 我才不跟那些無恥之徒來往呢.