The Collaborative International Dictionary of English v.0.48:

Tractable \Tract"a*ble\, a. [L. tractabilis, fr, tractare to
   draw violently, to handle, treat. See Treat, v. t.]
   1. Capable of being easily led, taught, or managed; docile;
      manageable; governable; as, tractable children; a
      tractable learner.
      [1913 Webster]

            I shall find them tractable enough.   --Shak.
      [1913 Webster]

   2. Capable of being handled; palpable; practicable; feasible;
      as, tractable measures. [Obs.] --Holder.
      [1913 Webster] --Tract"a*ble*ness, n. -- Tract"a/bly,
      adv.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tractable
    adj 1: easily managed (controlled or taught or molded);
           "tractable young minds"; "the natives...being...of an
           intelligent tractable disposition"- Samuel Butler [syn:
           tractable, manipulable] [ant: intractable]
    2: readily reacting to suggestions and influences; "a responsive
       student" [syn: amenable, tractable]

Moby Thesaurus II by Grady Ward, 1.0:

101 Moby Thesaurus words for "tractable":
   acquiescent, adaptable, adaptive, adjustable, agreeable,
   alacritous, amenable, ardent, bendable, bending, biddable,
   complaisant, compliant, conformable, consenting, content,
   convenient, cooperative, disposed, docile, ductile, eager,
   easygoing, elastic, enthusiastic, extensible, extensile,
   fabricable, facile, fain, favorable, favorably disposed,
   favorably inclined, feasible, fictile, flexible, flexile, flexuous,
   foolproof, formable, formative, forward, game, giving, governable,
   handleable, handy, impressible, impressionable, in the mind,
   in the mood, inclined, like putty, limber, lissome, lithe,
   lithesome, malleable, manageable, maneuverable, minded, moldable,
   obedient, other-directed, persuadable, persuasible, plastic,
   pliable, pliant, practical, predisposed, prompt, prone, quick,
   ready, ready and willing, receptive, responsive, sensitive,
   sequacious, shapable, springy, subdued, submissive, supple,
   susceptible, tame, tractile, untroublesome, well-disposed,
   well-inclined, whippy, wieldable, wieldy, willed, willing,
   willinghearted, willowy, workable, yielding, zealous