The Collaborative International Dictionary of English v.0.48:

Masterful \Mas"ter*ful\, a.
   1. Inclined to play the master; domineering; imperious;
      arbitrary. --Dryden.
      [1913 Webster]

   2. Having the skill or power of a master; indicating or
      expressing power or mastery.
      [1913 Webster]

            His masterful, pale face.             --Mrs.
                                                  Browning.
      [1913 Webster]

WordNet (r) 3.0 (2006):

masterful
    adj 1: having or revealing supreme mastery or skill; "a
           consummate artist"; "consummate skill"; "a masterful
           speaker"; "masterful technique"; "a masterly performance
           of the sonata"; "a virtuoso performance" [syn:
           consummate, masterful, masterly, virtuoso(a)]

Moby Thesaurus II by Grady Ward, 1.0:

120 Moby Thesaurus words for "masterful":
   Daedalian, U, absolute, absolutist, absolutistic, accomplished,
   adept, adroit, apt, arbitrary, archetypical, aristocratic,
   arrogant, artistic, authoritarian, authoritative, autocratic,
   bossy, bravura, brilliant, classic, clean, clever, consummate,
   coordinated, crack, crackerjack, cunning, cute, daedal, deft,
   despotic, developed, dexterous, dextrous, dictatorial, diplomatic,
   doctrinaire, dogmatic, dominating, domineering, elitist, excellent,
   exemplary, expert, exquisite, fancy, feudal, finished, first-rate,
   fully developed, good, goodish, graceful, grinding, handy,
   high and mighty, high-and-mighty, high-handed, hubristic,
   imperative, imperial, imperious, ingenious, lordly, magisterial,
   magistral, master, masterly, matchless, mature, matured, model,
   monocratic, neat, no mean, oppressive, overbearing, overruling,
   overweening, peerless, peremptory, perfected, polished, politic,
   preeminent, professional, proficient, quick, quintessential,
   quite some, ready, refined, repressive, resourceful, ripe, ripened,
   self-willed, severe, skilled, skillful, slick, some, statesmanlike,
   strict, stylish, superb, superior, superlative, suppressive,
   supreme, tactful, the compleat, the complete, transcendent,
   tyrannical, tyrannous, virtuoso, well-done, workmanlike