The Collaborative International Dictionary of English v.0.48:

Susceptibility \Sus*cep`ti*bil"i*ty\, n.; pl.
   Susceptibilities. [Cf. F. susceptibilit['e].]
   1. The state or quality of being susceptible; the capability
      of receiving impressions, or of being affected.
      [1913 Webster]

   2. Specifically, capacity for deep feeling or emotional
      excitement; sensibility, in its broadest acceptation;
      impressibility; sensitiveness.
      [1913 Webster]

   Magnetic susceptibility (Physics), the intensity of
      magnetization of a body placed in a uniform megnetic field
      of unit strength. --Sir W. Thomson.
      [1913 Webster]

   Syn: Capability; sensibility; feeling; emotion.
        [1913 Webster]

WordNet (r) 3.0 (2006):

susceptibility
    n 1: the state of being susceptible; easily affected [syn:
         susceptibility, susceptibleness] [ant: immunity,
         unsusceptibility]

Moby Thesaurus II by Grady Ward, 1.0:

152 Moby Thesaurus words for "susceptibility":
   a thing for, ability, ableness, accessibility, adaptability,
   adequacy, affectibility, affection, affectionateness, affectivity,
   affinity, agreeability, amativeness, amenability, amenableness,
   amorousness, aptitude, aptness, bendability, bent, bias,
   brightness, caliber, capability, capableness, capacity, cast,
   cleverness, competence, conatus, conduciveness, defenselessness,
   delicacy, delight, demonstrativeness, diathesis, disposition,
   docility, ductibility, ductility, eagerness, ecstasy, educability,
   efficacy, efficiency, elasticity, enchantment, exposure,
   extendibility, extensibility, facility, faculty, feeling for,
   fictility, fitness, flair, flexibility, flexility, flexuousness,
   formativeness, genius, give, goatishness, helplessness, horniness,
   impressibility, impressionability, inclination, influenceability,
   intelligence, leaning, liability, liking, limberness, limen,
   litheness, lovelornness, lovesickness, malleability, moldability,
   motivation, movability, nakedness, nonimmunity, open-mindedness,
   openness, openness to sensation, penchant, perceptibility,
   persuadability, perviousness, physical sensibility, plasticity,
   pliability, pliancy, predilection, predisposition, prejudice,
   probability, proclivity, proficiency, proneness, propensity,
   qualification, quickness, rapture, readiness, readiness of feeling,
   receptiveness, receptivity, responsiveness, romanticism,
   sensation level, sensibility, sensibleness, sensitiveness,
   sensitivity, sensitivity to, sentience, sentiency, sentimentality,
   sequacity, sexiness, soft spot, springiness, submissiveness,
   sufficiency, suggestibility, suppleness, susceptivity,
   swayableness, talent, teachability, teachableness, tendency,
   tensileness, tensility, the goods, the stuff,
   threshold of sensation, tractability, tractility, trainableness,
   tropism, turn, twist, vulnerability, warp, weakness, what it takes,
   willingness, willowiness