n. & v.
--n.
1. a layer of dirt, froth, or impurities etc. forming at the top of liquid, esp. in boiling or fermentation.
2 (foll. by of) the most worthless part of something.
3 colloq. a worthless person or group.
--v. (scummed, scumming)
1. tr. remove scum from; skim.
2 tr. be or form a scum on.
3 intr. (of a liquid) develop scum.
Derivatives:
scummy adj. (scummier, scummiest) adj.
Etymology: ME f. MLG, MDu. schum, OHG scum f. Gmc