Source : Webster's Revised Unabridged Dictionary (1913)

Actionable \Ac"tion*a*ble\, a. [Cf. LL. actionabilis. See
   {Action}.]
   That may be the subject of an action or suit at law; as, to
   call a man a thief is actionable.

Source : WordNet®

actionable
     adj : affording grounds for legal action; "slander is an
           actionable offense"