Is there a difference between these two words? To me, it seems that undistinguishable is more where you can’t tell what it is, and indistinguishable seems to be where they’re the same. It seems a lot of places list them as synonyms though.
I’m a native English speaker, and I’ve never heard of “undistinguishable”. I searched for undistinguishable and Google replied with:
Did you mean: indistinguishable
identical: exactly alike; incapable of being perceived as different; “rows of identical houses”; “cars identical except for their license plates”; “they wore indistinguishable hats”
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”