Source : Webster's Revised Unabridged Dictionary (1913)

Perceivable \Per*ceiv"a*ble\, a.
   Capable of being perceived; perceptible. -- {Per*ceiv"a*bly},
   adv.

Source : WordNet®

perceivable
     adj 1: capable of being perceived especially by sight or hearing;
            "perceivable through the mist"
     2: capable of being apprehended or understood [syn: {apprehensible},
         {intelligible}, {graspable}, {understandable}]