1. Quite good
   "The food at the new restaurant was not bad";
   - not so bad [informal], fair
    
2. Excellent
   "he did a not bad job";
   - bang-up [N. Amer, informal], bully [informal], corking [Brit, informal], cracking [Brit, informal], dandy [informal], great, groovy [informal], keen, neat, nifty [informal], peachy, slap-up [informal], swell [informal], smashing [Brit, informal], old, not half bad [informal], grouse [Austral, NZ, informal], ripper [Austral, informal], lovely

See also: good

Encyclopedia: Not bad