The Collaborative International Dictionary of English v.0.48:

disability \dis`a*bil"i*ty\, n.; pl. Disabilities.
   1. State of being disabled; deprivation or want of ability;
      absence of competent physical, intellectual, or moral
      power, means, fitness, and the like.
      [1913 Webster]

            Grossest faults, or disabilities to perform what was
            covenanted.                           --Milton.
      [1913 Webster]

            Chatham refused to see him, pleading his disability.
                                                  --Bancroft.
      [1913 Webster]

   2. Want of legal qualification to do a thing; legal
      incapacity or incompetency.
      [1913 Webster]

            The disabilities of idiocy, infancy, and coverture.
                                                  --Abbott.

   Syn: Weakness; inability; incompetence; impotence;
        incapacity; incompetency; disqualification.

   Usage: -- Disability, Inability. Inability is an inherent
          want of power to perform the thing in question;
          disability arises from some deprivation or loss of the
          needed competency. One who becomes deranged is under a
          disability of holding his estate; and one who is made
          a judge, of deciding in his own case. A man may
          decline an office on account of his inability to
          discharge its duties; he may refuse to accept a trust
          or employment on account of some disability prevents
          him from entering into such engagements.
          [1913 Webster]

WordNet (r) 3.0 (2006):

disability
    n 1: the condition of being unable to perform as a consequence
         of physical or mental unfitness; "reading disability";
         "hearing impairment" [syn: disability, disablement,
         handicap, impairment]