The Collaborative International Dictionary of English v.0.48:

Reluctance \Re*luc"tance\ (r?-l?k"tans), Reluctancy
\Re*luc"tan*cy\ (-tan-s?), n. [See Reluctant.]
   1. The state or quality of being reluctant; repugnance;
      aversion of mind; unwillingness; -- often followed by an
      infinitive, or by to and a noun, formerly sometimes by
      against. "Tempering the severity of his looks with a
      reluctance to the action." --Dryden.

   Syn: Syn. See Dislike.
        [1913 Webster]

              He had some reluctance to obey the summons. --Sir
                                                  W. Scott.
        [1913 Webster]

              Bear witness, Heaven, with what reluctancy
              Her helpless innocence I doom to die. --Dryden.
        [1913 Webster]

   2. (Elec.) Magnetic resistance, being equal to the ratio of
      magnetomotive force to magnetic flux.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

reluctance
    n 1: (physics) opposition to magnetic flux (analogous to
         electric resistance)
    2: a certain degree of unwillingness; "a reluctance to commit
       himself"; "his hesitancy revealed his basic indisposition";
       "after some hesitation he agreed" [syn: reluctance,
       hesitancy, hesitation, disinclination, indisposition]

Moby Thesaurus II by Grady Ward, 1.0:

103 Moby Thesaurus words for "reluctance":
   antipathy, averseness, aversion, backwardness,
   capacitive reactance, cautiousness, challenge, circumspection,
   combative reaction, complaint, counteraction, creeping,
   cursoriness, defiance, deliberateness, deliberation, demur,
   disagreement, disinclination, dislike, disobedience, dispute,
   disrelish, dissent, dissentience, distaste, drawl,
   electric resistance, foot-dragging, fractiousness,
   grudging consent, grudgingness, hesitancy, idleness, impedance,
   indisposedness, indisposition, indocility, indolence,
   inductive reactance, inertia, inertness, intractableness,
   lack of enthusiasm, lack of zeal, languor, laziness, leisureliness,
   lentitude, lentor, magnetic reluctance, mutinousness, negativism,
   nolition, noncooperation, objection, obstinacy, ohm, ohmage,
   opposition, passive resistance, perfunctoriness, pokiness, protest,
   reactance, reaction, rebuff, recalcitrance, recalcitrancy,
   recalcitration, refractoriness, refusal, reluctivity, remonstrance,
   renitence, renitency, repellence, repellency, repugnance, repulse,
   repulsion, resistance, revolt, skin effect, slackness, sloth,
   slowness, sluggardy, sluggishness, specific reluctance, stand,
   stubbornness, sulk, sulkiness, sulks, sullenness,
   surface resistance, tentativeness, uncooperativeness, unenthusiasm,
   unwillingness, volume resistance, withstanding