indistinguishable

in- +‎ distinguishable

indistinguishable (comparative more indistinguishable, superlative most indistinguishable)

1. Not distinguishable; not capable of being perceived, known, or discriminated as separate and distinct
   • 1950 May, M. D. Greville and G. O. Holt, “A Forgotten Junction in Westmorland”, in Railway Magazine, page 330:

     The banks of the old railway are now so thickly overgrown with trees as to be almost indistinguishable from the surrounding countryside, and the most obvious landmarks are the walls of a bridge over a lane, and stone bridge, still intact, where a cart road crosses the cutting, close to the site of the former Clifton South Junction.

   • 1973, Arthur C. Clarke, Profiles of the Future (revised):

     Any sufficiently advanced technology is indistinguishable from magic

2. Not capable of being perceived or known.

• distinguishable
• (antonym(s) of “not capable of being perceived as separate and distinct”): fuzzy, ill-defined, indistinct; see also Thesaurus:indistinct
• (antonym(s) of “not capable of being perceived”): invisible, undetectable

• indistinguishability

indistinguishable (plural indistinguishables)

1. Any of a set of things that cannot be distinguished.