1. Spoiled and covered with eggs and larvae of flies
   "flyblown meat";
   - maggoty
    
2. Foul and run-down and repulsive
   "a flyblown bar on the edge of town";
   - squalid, sordid, skeevy [US, informal], skanky [informal], grotty [Brit, informal]
    
3. Blemished, especially of reputation
   "a flyblown reputation"

See also: blemished, dirty, soiled, stale, unclean