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]