The Collaborative International Dictionary of English v.0.48:

Manageable \Man"age*a*ble\, a.
   Such as can be managed or used; suffering control;
   governable; tractable; subservient; as, a manageable horse.
   [1913 Webster]

   Syn: Governable; tractable; controllable; docile.
        [1913 Webster] -- Man"age*a*ble*ness, n. --
        Man"age*a*bly, adv.
        [1913 Webster]

WordNet (r) 3.0 (2006):

manageableness
    n 1: capable of being managed or controlled [syn:
         manageability, manageableness]