The Collaborative International Dictionary of English v.0.48:

Sensitive \Sen"si*tive\, a. [F. sensitif. See Sense.]
   1. Having sense of feeling; possessing or exhibiting the
      capacity of receiving impressions from external objects;
      as, a sensitive soul.
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   2. Having quick and acute sensibility, either to the action
      of external objects, or to impressions upon the mind and
      feelings; highly susceptible; easily and acutely affected.
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            She was too sensitive to abuse and calumny.
                                                  --Macaulay.
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   3.
      (a) (Mech.) Having a capacity of being easily affected or
          moved; as, a sensitive thermometer; sensitive scales.
      (b) (Chem. & Photog.) Readily affected or changed by
          certain appropriate agents; as, silver chloride or
          bromide, when in contact with certain organic
          substances, is extremely sensitive to actinic rays.
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   4. Serving to affect the sense; sensible. [R.]
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            A sensitive love of some sensitive objects.
                                                  --Hammond.
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   5. Of or pertaining to sensation; depending on sensation; as,
      sensitive motions; sensitive muscular motions excited by
      irritation. --E. Darwin.
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   Sensitive fern (Bot.), an American fern (Onoclea
      sensibilis), the leaves of which, when plucked, show a
      slight tendency to fold together.

   Sensitive flame (Physics), a gas flame so arranged that
      under a suitable adjustment of pressure it is exceedingly
      sensitive to sounds, being caused to roar, flare, or
      become suddenly shortened or extinguished, by slight
      sounds of the proper pitch.

   Sensitive joint vetch (Bot.), an annual leguminous herb
      (Aeschynomene hispida), with sensitive foliage.

   Sensitive paper, paper prepared for photographic purpose by
      being rendered sensitive to the effect of light.

   Sensitive plant. (Bot.)
      (a) A leguminous plant (Mimosa pudica, or Mimosa
          sensitiva, and other allied species), the leaves of
          which close at the slightest touch.
      (b) Any plant showing motions after irritation, as the
          sensitive brier (Schrankia) of the Southern States,
          two common American species of Cassia (Cassia
          nictitans, and Cassia Chamaecrista), a kind of
          sorrel (Oxalis sensitiva), etc.
          [1913 Webster] -- Sen"si*tive*ly, adv. --
          Sen"si*tive*ness, n.
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WordNet (r) 3.0 (2006):

sensitiveness
    n 1: sensitivity to emotional feelings (of self and others)
         [syn: sensitivity, sensitiveness]
    2: (physiology) responsiveness to external stimuli; the faculty
       of sensation; "sensitivity to pain" [syn: sensitivity,
       sensitiveness, sensibility]
    3: the ability to respond to physical stimuli or to register
       small physical amounts or differences; "a galvanometer of
       extreme sensitivity"; "the sensitiveness of Mimosa leaves
       does not depend on a change of growth" [syn: sensitivity,
       sensitiveness]
    4: the ability to respond to affective changes in your
       interpersonal environment [syn: sensitivity,
       sensitiveness] [ant: insensitiveness, insensitivity]