Source : Webster's Revised Unabridged Dictionary (1913)

Appreciable \Ap*pre"ci*a*ble\, a. [Cf. F. appr['e]ciable.]
   Capable of being appreciated or estimated; large enough to be
   estimated; perceptible; as, an appreciable quantity. --
   {Ap*pre"ci*a*bly}, adv.

Source : WordNet®

appreciable
     adj : enough to be estimated or measured; "appreciable amounts of
           noxious wastes are dumped into the harbor"