The Collaborative International Dictionary of English v.0.48:
indistinguishability \in`dis*tin`guish*a*bil"i*ty\ n. smilarity too close to be distinguished; exact sameness. Syn: identity, identicalness. [WordNet 1.5]WordNet (r) 3.0 (2006):
indistinguishability n 1: exact sameness; "they shared an identity of interests" [syn: identity, identicalness, indistinguishability]