The Collaborative International Dictionary of English v.0.48:

Suasible \Sua"si*ble\, a. [L. suadere, suasum, to persuade.]
   Capable of being persuaded; easily persuaded.
   [1913 Webster]

WordNet (r) 3.0 (2006):

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