WordWeb Online

1. Very unpleasant or offensive
   "a grotty little play"
    
2. Showing signs of wear and tear
   "a grotty old overcoat";
   - moth-eaten, ratty, shabby, tatty [informal]
    
3. Somewhat ill, feeling or being in bad health
   - ailing, indisposed, peaked, poorly, sickly, unwell, under the weather [informal], seedy [archaic], off-colour [Brit, informal], out of sorts [informal], crook [Austral, NZ, informal]

Derived forms: grottier, grottiest

See also: awful, ill, nasty, sick, worn