The Collaborative International Dictionary of English v.0.48:

Malleable \Mal"le*a*ble\, a. [F. mall['e]able, fr. LL. malleare
   to hammer. See Malleate.]
   1. Capable of being extended or shaped by beating with a
      hammer, or by the pressure of rollers; -- applied to
      metals.
      [1913 Webster]

   2. Capable of being influenced to behave as desired;
      tractable; -- used mostly of children.
      [PJC]

   Malleable iron, iron that is capable of extension or of
      being shaped under the hammer; decarbonized cast iron. See
      under Iron.

   Malleable iron castings, articles cast from pig iron and
      made malleable by heating then for several days in the
      presence of some substance, as hematite, which deprives
      the cast iron of some of its carbon.
      [1913 Webster]

WordNet (r) 3.0 (2006):

malleable
    adj 1: easily influenced [syn: ductile, malleable]
    2: capable of being shaped or bent or drawn out; "ductile
       copper"; "malleable metals such as gold"; "they soaked the
       leather to made it pliable"; "pliant molten glass"; "made of
       highly tensile steel alloy" [syn: ductile, malleable,
       pliable, pliant, tensile, tractile]

Moby Thesaurus II by Grady Ward, 1.0:

114 Moby Thesaurus words for "malleable":
   able to adapt, accessible, acquiescent, adaptable, adaptive,
   adjustable, alterable, alterative, amenable, apt, bendable,
   bending, biddable, bright, changeable, checkered, clever,
   complaisant, compliant, conformable, convenient, docile, ductile,
   educable, elastic, ever-changing, extensible, extensile,
   fabricable, facile, feasible, fictile, flexible, flexile, flexuous,
   fluid, foolproof, formable, formative, giving, governable, handy,
   impermanent, impressible, impressionable, influenceable,
   instructable, intelligent, kaleidoscopic, like putty, limber,
   lissome, lithe, lithesome, manageable, maneuverable, many-sided,
   metamorphic, mobile, modifiable, moldable, motivated, movable,
   mutable, nonuniform, obedient, open, open-minded, other-directed,
   permutable, persuadable, persuasible, pervious, plastic, pliable,
   pliant, practical, protean, proteiform, quick, ready, receptive,
   resilient, responsive, ripe for instruction, rubbery, schoolable,
   sensitive, sequacious, shapable, springy, suasible, submissive,
   suggestible, supple, susceptible, swayable, teachable,
   thirsty for knowledge, tractable, tractile, trainable,
   transformable, transient, transitory, untroublesome, variable,
   weak, whippy, wieldable, wieldy, willing, willowy, yielding