'Imperceptibility' definitions:

Definition of 'imperceptibility'

From: WordNet
noun
The property of being imperceptible by the mind or the senses [ant: perceptibility]

Definition of 'Imperceptibility'

From: GCIDE
  • Imperceptibility \Im`per*cep`ti*bil"i*ty\, n. The state or quality of being imperceptible. [1913 Webster]