mass noun
1- a layer of dirt or froth on the surface of a liquid浮垢, 浮渣：
green scum found on stagnant pools.
积水潭表面发现的绿色浮垢。
1.1
- informal a worthless or contemptible person or group of people〈非正式〉渣滓, （一群）卑贱的人：
you drug dealers are the scum of the earth.
你们毒贩是社会的渣滓。
(scummed, scumming)with obj.
1- form a layer of dirt or froth on (a liquid)形成浮垢（或浮渣）：
litter scummed the surface of the water.
乱扔的杂物在水面形成浮渣。
1.1
- no obj.(of a liquid) become covered with a layer of dirt or froth（液体）覆盖着浮渣（或浮垢）：
the lagoon scummed over.
礁湖上漂满了浮垢。
派生词
scummy
adjective （scummier, scummiest）词源
Middle English:from Middle Low German， Middle Dutch schūm, of Germanic origin.