The Collaborative International Dictionary of English v.0.48:

mangy \man"gy\, a. [Compar. mangier; superl. mangiest.] [F.
   mang['e], p. p. of manger to eat. See Manger.]
   1. Infected with the mange; scabby.
      [1913 Webster]

   2. Shabby; worn-out; seedy; run-down; squalid; as, a mangy
      old coat; a mangy tavern.
      [PJC]

WordNet (r) 3.0 (2006):

mangy
    adj 1: having many worn or threadbare spots in the nap; "a mangy
           carpet"; "a mangy old fur coat" [syn: mangy, mangey]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "mangy":
   abject, base, contemptible, decrepit, despicable, dingy, dirty,
   disreputable, down-at-heel, filthy, ignominious, low, mean,
   miserable, moth-eaten, nasty, odious, poor, repulsive, scruffy,
   scurvy, seedy, shabby, sleazy, slovenly, sorry, squalid, tattered,
   unkempt, wretched