The Collaborative International Dictionary of English v.0.48:

Incapacity \In`ca*pac"i*ty\, n.; pl. Incapacities. [Cf. F.
   incapacit['e].]
   [1913 Webster]
   1. Lack of capacity; lack of physical or intellectual power;
      inability.
      [1913 Webster]

   2. (Law) Lack of legal ability or competency to do, give,
      transmit, or receive something; inability;
      disqualification; as, the inacapacity of minors to make
      binding contracts, etc.

   Syn: Inability; incapability; incompetency; unfitness;
        disqualification; disability.
        [1913 Webster]

WordNet (r) 3.0 (2006):

incapacity
    n 1: lack of intellectual power [ant: capacity, mental
         ability]
    2: lack of physical or natural qualifications [ant: capacity]