NOUN (2)

1. lack of intellectual power;

2. lack of physical or natural qualifications;

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]

Moby Thesaurus II by Grady Ward, 1.0:

82 Moby Thesaurus words for "incapacity":
   Urdummheit, brainlessness, caducity, decrepitude, disability,
   disablement, disqualification, foolishness, ignorance, imbecility,
   inability, inadeptness, inadequacy, inaptitude, inaptness,
   inattentiveness, incapability, incapacitation, incompetence,
   incompetency, indexterity, ineffectiveness, ineffectuality,
   inefficacy, inefficiency, ineptitude, ineptness, infancy,
   inferiority, infirmity, insipidity, instability, insufficiency,
   invalidism, irrationality, lackbrainedness, lackwittedness,
   legal incapacity, low IQ, maladjustment, maladroitness, mediocrity,
   mental weakness, mindlessness, minority, pedestrianism,
   primal stupidity, reasonlessness, ricketiness, rustiness, senility,
   senselessness, shakiness, skill-lessness, slackmindedness,
   slackwittedness, thoughtlessness, unaptness, uncleverness,
   undeftness, undexterousness, undextrousness, unfirmness, unfitness,
   unfittedness, unintellectuality, unintelligence, unproficiency,
   unschooledness, unskillfulness, unsoundness, unsteadiness,
   unsturdiness, unsubstantiality, untrainedness, unwisdom,
   unwiseness, vapidity, wardship, wateriness, wishy-washiness,
   witlessness