The Collaborative International Dictionary of English v.0.48:

Crummy \Crum"my\ (kr[u^]m"m[y^]), a.
   1. Full of crumb or crumbs.
      [1913 Webster]

   2. Soft, as the crumb of bread is; not crusty.
      [1913 Webster]

   3. of very poor quality. [informal]

   Syn: bum, cheap, cheesy, chintzy, crummy, punk, sleazy,
        tinny. [WordNet 1.5]

WordNet (r) 3.0 (2006):

crummy
    adj 1: of very poor quality; flimsy [syn: bum, cheap,
           cheesy, chintzy, crummy, punk, sleazy, tinny]

Moby Thesaurus II by Grady Ward, 1.0:

88 Moby Thesaurus words for "crummy":
   abject, abominable, arrant, atrocious, barfy, base, beggarly,
   beneath contempt, bum, cheap, cheesy, common, contemptible, crappy,
   creepy, debased, degraded, depraved, despicable, dirty, disgusting,
   execrable, flagrant, foul, fulsome, gaudy, gimcracky, godawful,
   goshawful, grave, grim, gross, hairy, heinous, icky, little, low,
   low-down, lumpen, mangy, mean, measly, meretricious, miserable,
   monstrous, nefarious, obnoxious, odious, paltry, pathetic, petty,
   pitiable, pitiful, poky, poor, punk, putrid, rank, reptilian,
   rubbishy, sad, scabby, scrubby, scruffy, scummy, scurvy, scuzzy,
   shabby, shitty, shoddy, small, sorry, squalid, stinking, stinky,
   trashy, trumpery, two-for-a-cent, two-for-a-penny, twopenny,
   twopenny-halfpenny, unmentionable, valueless, vile, vomity,
   worthless, wretched, yecchy