scum /skʌm/ BrE AmE noun
[ Date: 1300-1400 ; Language: Middle Dutch ; Origin: schum ]
1 . [uncountable] an unpleasant dirty substance that forms on the surface of water:
a pond covered with green scum
2 . [plural] informal nasty unpleasant people:
Scum like that should be locked away!
People like that are the scum of the earth.
—scummy adjective