[1] : The Collaborative International Dictionary of English v.0.48

unperceivable \unperceivable\
   see perceivable.
see also:
perceivable 

[2] : WordNet (r) 2.0

unperceivable
     adj : impossible or difficult to perceive by the mind or senses;
           "an imperceptible drop in temperature"; "an
           imperceptible nod"; "color is unperceivable to the
           touch" syn: imperceptible ant: perceptible
see also:
imperceptible perceptible 

Unperceivable >> U Words
Unperceivable, definition of term: Unperceivable
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