The Collaborative International Dictionary of English v.0.48:

Persuasible \Per*sua"si*ble\, a. [Cf. L. persuasibilis
   persuasive, F. persuasible persuasible.]
   1. Capable of being persuaded; persuadable.
      [1913 Webster]

   2. Persuasive. [Obs.] --Bale.
      [1913 Webster] -- Per*sua"si*ble*ness, n. --
      Per*sua"si*bly, adv.
      [1913 Webster]

WordNet (r) 3.0 (2006):

persuasible
    adj 1: being susceptible to persuasion [syn: convincible,
           persuadable, persuasible, suasible]