The Collaborative International Dictionary of English v.0.48:

Numbness \Numb"ness\, n.
   The condition of being numb; that state of a living body in
   which it loses, wholly or in part, the power of feeling or
   motion.
   [1913 Webster]

WordNet (r) 3.0 (2006):

numbness
    n 1: partial or total lack of sensation in a part of the body; a
         symptom of nerve damage or dysfunction
    2: the trait of lacking enthusiasm for or interest in things
       generally [syn: apathy, indifference, numbness,
       spiritlessness]