Definition of unperceptable in US English:

unperceptable

adjective

rare, non-standard
  • = unperceptible.

Origin

Late 17th century; earliest use found in John Humfrey (bap. 1621, d. 1719), clergyman and ejected minister. From un- + classical Latin percept-, past participial stem of percipere perceive + -able.

Pronunciation

unperceptable

/(ˌ)ʌnpəˈsɛptəbl/