The Collaborative International Dictionary of English v.0.48:

Apprehensible \Ap`pre*hen"si*ble\, a. [L. apprehensibilis. See
   Apprehend.]
   Capable of being apprehended or conceived. "Apprehensible by
   faith." --Bp. Hall. -- Ap`*pre*hen"si*bly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

apprehensible
    adj 1: capable of being apprehended or understood [syn:
           apprehensible, intelligible, graspable,
           perceivable, understandable]