Definitions
1.NounA layer of impurities that accumulates at the surface of a liquid (especially molten metal or water)."During smelting, scum rises to the surface and is then removed by the smelter."
2.NounA greenish water vegetation (such as algae), usually found floating on the surface of ponds"These organisms form scum in large quantities."
3.NounThe topmost liquid layer of a cesspool or septic tank.
4.NounSemen. .mw-parser-output .defdate{font-size:smaller}
5.NounA reprehensible person or persons."People who sell used-up pens are scum, just total low-lives."
6.VerbTo remove the layer of scum from (a liquid etc.).
7.VerbTo remove (something) as scum.
8.VerbTo become covered with scum.
9.VerbTo scour (the land, sea, etc.).
10.VerbTo gather together, as scum.
11.VerbTo startscum or savescum.