Source : Webster's Revised Unabridged Dictionary (1913)

Perceptibility \Per*cep`ti*bil"i*ty\, n. [Cf. F.
   perceptibilit['e].]
   1. The quality or state of being perceptible; as, the
      perceptibility of light or color.

   2. Perception. [R.] --Dr. H. More.

Source : WordNet®

perceptibility
     n : the property of being perceptible [ant: {imperceptibility}]