The Collaborative International Dictionary of English v.0.48:

Insensibility \In*sen`si*bil"i*ty\, n. [Cf. F.
   insensibilit['e].]
   [1913 Webster]
   1. The state or quality of being insensible; lack of
      sensibility; torpor; unconsciousness; as, the
      insensibility produced by a fall, or by opiates.
      [1913 Webster]

   2. Lack of tenderness or susceptibility of emotion or
      passion; dullness; stupidity.

   Syn: Dullness; numbness; unfeelingness; stupidity; torpor;
        apathy; impassiveness; indifference.
        [1913 Webster]

WordNet (r) 3.0 (2006):

insensibility
    n 1: a lack of sensibility [ant: aesthesia, esthesia,
         sensibility]
    2: devoid of passion or feeling; hardheartedness [syn:
       unfeelingness, callousness, callosity, hardness,
       insensibility]

Moby Thesaurus II by Grady Ward, 1.0:

92 Moby Thesaurus words for "insensibility":
   abstraction, abulia, alienation, anxiety, anxiety equivalent,
   anxiety state, apathy, blindness, casualness, catatonic stupor,
   compulsion, crudity of intellect, deafness, dejection, depression,
   detachment, dim-sightedness, elation, emotionalism, euphoria,
   folie du doute, hypochondria, hysteria, hysterics, impassivity,
   imperceptiveness, impercipience, imprudence, inanimateness,
   inanimation, incognizance, incomprehension, indifference,
   indiscreetness, indiscretion, indiscriminateness, indiscrimination,
   inertness, insensibleness, insensitivity, insentience,
   lack of feeling, lack of refinement, lethargy, lifelessness, mania,
   melancholia, mental distress, mindlessness, nearsightedness,
   nonrealization, nonrecognition, nonunderstanding, oblivion,
   obliviousness, obsession, pathological indecisiveness, phlegm,
   preoccupation, promiscuity, promiscuousness, psychalgia,
   psychomotor disturbance, purblindness, senselessness,
   shortsightedness, stoicism, stolidity, stupor, syncretism,
   tactlessness, tic, twitching, unapprehendingness, unawareness,
   unconsciousness, uncriticalness, undiscerningness,
   undiscriminatingness, undiscriminativeness, unfastidiousness,
   unfeelingness, unmeticulousness, unmindfulness, unparticularness,
   unperceptiveness, unpreciseness, unresponsiveness, unselectiveness,
   untactfulness, unwittingness, withdrawal