Definition of unperceptible in US English:

unperceptible

adjective

  • Imperceptible.

Origin

Late Middle English; earliest use found in John Trevisa (c1342–?1402), translator. From un- + perceptible (although this is first attested later), originally after post-classical Latin imperceptibilis imperceptible.

Pronunciation

unperceptible

/(ˌ)ʌnpəˈsɛptɪbl/