scum

Etymology

From Middle English scum, scome, skum, skome, scumme, from Middle Dutch schūme (“foam”), from Proto-Germanic *skūmaz (“froth, foam”), from Proto-Indo-European *skew- (“to cover, conceal”). Cognate with Dutch schuim (“foam”), German Schaum (“foam”), Danish and Swedish skum (“foam”). Compare also French écume (“scum”), Italian schiuma (“foam”), Walloon schome (“scum, foam”), Lithuanian šamas (“catfish”) and skanus (“tasty”) from the same Germanic source. Related to skim.

noun

1. (uncountable) A 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. (uncountable) A greenish water vegetation (such as algae), usually found floating on the surface of ponds
   These organisms form scum in large quantities.
3. The topmost liquid layer of a cesspool or septic tank.
4. (uncountable, slang, chiefly US) Semen.
   Horse, who was always talking about facts, said, “Man, that can't be scum, ’cause scum is white.” 1965, Claude Brown, Manchild in the Promised Land, New York: New American Library, →OCLC, page 80
5. (derogatory, slang) A reprehensible person or persons.
   People who sell used-up pens are scum, just total low-lives.

verb

1. To remove the layer of scum from (a liquid etc.).
2. To remove (something) as scum.
3. To become covered with scum.
   Take the smallest Cucumbers you can get, and as free from Spots as possible, put them into a strong Salt and Water for nine or ten Days, or 'till they are quite Yellow, and stir them twice a Day at least, or they will scum over, and grow soft 1769, Elizabeth Raffald, The Experienced English House-keeper, pages 321–322
4. (obsolete) To scour (the land, sea, etc.).
5. (obsolete) To gather together, as scum.
   A great majority of the members are scummed together from the Jacobinical dregs of former periods of the revolution. 1815, Rudolf Ackerman, Frederic Shoberl, The Repository of Arts, Literature, Commerce, Manufactures, Fashions and Politics
6. (video games, informal) To startscum or savescum.