- Not distinguishable; not capable of being perceived, known, or discriminated as separate and distinct
- Any sufficiently advanced technology is indistinguishable from magic — Arthur C. Clarke 
- Not capable of being perceived or known.
Part or all of this entry has been imported from the 1913 edition of Webster’s Dictionary, which is now free of copyright and hence in the public domain. The imported definitions may be significantly out of date, and any more recent senses may be completely missing.
(See the entry for indistinguishable in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913.)