indiscernible
[adjective]
Synonyms: imperceptible, impalpable, imponderable, inappreciable, insensible, intangible, unapparent, unappreciable, unobservable, unperceivable

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Antonyms: discernible, distinguishable

[TahlilGaran] English Synonym Dictionary ▲

in‧dis‧cer‧ni‧ble /ˌɪndɪˈsɜːnəbəl◂, ˌɪndɪˈsɜːnɪbəl◂ $ -ɜːr-/ adjective
very difficult to see, hear, or notice:
The path was almost indiscernible in the mist.

[TahlilGaran] Dictionary of Contemporary English ▲