A reprehensible person or persons.
Semen.
A layer of impurities that accumulates at the surface of a liquid (especially molten metal or water).
A greenish water vegetation (such as algae), usually found floating on the surface of ponds
The topmost liquid layer of a cesspool or septic tank.
To remove (something) as scum.
To startscum or savescum.
To remove the layer of scum from (a liquid etc.).
To become covered with scum.
An unclean, or otherwise undesirable person.