Synonyms for Scum:

n.

horror, public nuisance, public enemy number one, (the) scum of the earth, know-all, loudmouth, yob. over, lumpenproletariat, dreg, riffraff, rich, the great unwashed, rabble, tag and rag, ragtag and bobtail, scum of the earth. bad person (noun)
dregs.
dirt (noun)
dust, dirt, muck, murk, smut, grime, filth, grunge, mess.
froth (noun)
impurities, film.
group (noun)
trash.
people who are bad, despicable (noun)
rabble, dregs, scum of the earth, riffraff, trash.
residue (noun)
chaff, grounds, remainder, residue, precipitate, afterimage, detritus, artifact, debris, remnant, sawdust, sediment, afterglow, slag, vestige, Filings, leftovers, dross, dregs.
scum (noun)
trash.
superficial impurities, dirt (noun)
dross, film, residue.

Other synonyms:

film, ragtag and bobtail, lumpenproletariat. dreg, rabble, riffraff. dirt
dust, dirt, muck, murk, smut, grime, filth, grunge, mess.
Other relevant words:
film, muck, rabble, riffraff, murk, dreg, grime, dust, filth, ragtag and bobtail, smut, trash, dirt, lumpenproletariat, the great unwashed, tag and rag, scum of the earth, mess, grunge.

Usage examples for scum

  1. Salute, first, you frozen- faced scum of the earth! – Shorty McCabe by Sewell Ford
  2. For the composition, too, I admit the Algerine community resembles that of France,- being formed out of the very scum scandal, disgrace, and pest of the Turkish Asia. – The Works of the Right Honourable Edmund Burke, Vol. V. (of 12) by Edmund Burke
  3. Both alike, whether spiritual or temporal, are of that poor scum of humanity which merits nothing but contempt; whereas Mas'aniello is heroic, stained by no unworthy action, and bearing himself right nobly in a crisis as wondrous as any in the whole history of man. – Naples Past and Present by Arthur H. Norway