Douglas Harper's Etymology Dictionary
1580s, from un- (1) ânotâ + distinguishable.
Wiktionary
a. 1 imperceptible; indistinct. 2 indistinguishable.
WordNet
adj. 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" [syn: indistinguishable] [ant: distinguishable]
Usage examples of "undistinguishable".
It is by this time mere vegetable mould and undistinguishable pond shore, through which rushes and flags have pushed up.
Something that he saw, something that was said, an undistinguishable something refused to let his mind slow down and rest.
The garthmaster reversed the tool, bringing its heavy head rather than cutting blade down on the objects there, battering and breaking them into an undistinguishable mass of crushed material, while the Speaker continued to chant.
His helmet com-unit must have been on, for, while his natural voice could only have been an undistinguishable murmur to those in hiding, his words were loud in their ears.
He moaned again and then uttered some undistinguishable words through torn lips as his puffed and swollen eyes turned up towards them.