[1] : The Collaborative International Dictionary of English v.0.48

scummy \scum"my\, a.
   covered with scum; of the nature of scum. --sir p. sidney.
   1913 webster

[2] : WordNet (r) 2.0

scummy
     adj 1: of the most contemptible kind; "abject cowardice"; "a low
            stunt to pull"; "a low-down sneak"; "his miserable
            treatment of his family"; "you miserable skunk"; "a
            scummy rabble"; "a scurvy trick" syn: abject, low,
             low-down, miserable, scurvy
     2: covered with scum; "the scummy surface of the polluted pond"
see also:
abject low low-down miserable scurvy 

[3] : Moby Thesaurus II by Grady Ward, 1.0

125 moby thesaurus words for "scummy":
   abject, abominable, arrant, atrocious, barfy, base, beggarly,
   beneath contempt, cheap, cheesy, common, contemptible, crappy,
   crummy, debased, degraded, depraved, despicable, dirty, disgusting,
   execrable, fecal, feculent, fetid, filmy, filthy, flagrant,
   flyblown, foliaceous, foliated, foul, fulsome, gaudy, gimcracky,
   gloppy, grave, gross, gunky, heinous, icky, in layers, lamellar,
   lamellate, lamellated, lamelliform, laminate, laminated, laminous,
   leaflike, leafy, little, low, low-down, lumpen, maggoty,
   malodorous, mangy, mean, measly, membranous, mephitic,
   meretricious, miserable, monstrous, mucky, nasty, nauseating,
   nefarious, obnoxious, odious, ordurous, paltry, pathetic, petty,
   pitiable, pitiful, poky, poor, puky, putrid, rank, reptilian,
   repulsive, rotten, rubbishy, sad, scabby, scrubby, scruffy, scurfy,
   scurvy, scuzzy, shabby, shitty, shoddy, slabby, slimy, sloppy,
   sloshy, sludgy, slushy, small, sorry, spathic, spathose, sposhy,
   squalid, stratified, stratiform, three-ply, trashy, trumpery,
   two-for-a-cent, two-for-a-penny, two-ply, twopenny,
   twopenny-halfpenny, unmentionable, valueless, vile, vomity, wormy,
   worthless, wretched, yecchy

Scummy >> S Words
Scummy, definition of term: Scummy
scummy_pag1.html