The Collaborative International Dictionary of English v.0.48:

Infirmity \In*firm"i*ty\, n.; pl. Infirmities. [L. infirmitas
   : cf. F. infirmite. See Infirm, a.]
   1. The state of being infirm; feebleness; an imperfection or
      weakness; esp., an unsound, unhealthy, or debilitated
      state; a disease; a malady; as, infirmity of body or mind.
      [1913 Webster]

            'T is the infirmity of his age.       --Shak.
      [1913 Webster]

   2. A personal frailty or failing; foible; eccentricity; a
      weakness or defect.
      [1913 Webster]

            Will you be cured of your infirmity ? --Shak.
      [1913 Webster]

            A friend should bear his friend's infirmities.
                                                  --Shak.
      [1913 Webster]

            The house has also its infirmities.   --Evelyn.

   Syn: Debility; imbecility; weakness; feebleness; failing;
        foible; defect; disease; malady. See Debility.
        [1913 Webster]

WordNet (r) 3.0 (2006):

infirmity
    n 1: the state of being weak in health or body (especially from
         old age) [syn: infirmity, frailty, debility,
         feebleness, frailness, valetudinarianism]