indistinguishable in WordNet English dictionary

1. exactly alike; incapable of being perceived as different
   "rows of identical houses"; "cars identical except for their license plates"; "they wore indistinguishable hats"
   identical  indistinguishable 
   
2. not capable of being distinguished or differentiated
   "the two specimens are actually different from each other but the differences are almost indistinguishable"; "the twins were indistinguishable"; "a colorless person quite indistinguishable from the colorless mass of humanity"
   indistinguishable  undistinguishable