The Collaborative International Dictionary of English v.0.48:

frailty \frail"ty\ (fr[=a]l"t[y^]), n.; pl. frailties
   (fr[=a]l"t[i^]z). [OE. frelete, freilte, OF. frailet['e], fr.
   L. fragilitas. See Frail, a., and cf. Fragility.]
   1. The condition or quality of being frail, physically,
      mentally, or morally; frailness; infirmity; weakness of
      resolution; liableness to be deceived or seduced.
      [1913 Webster]

            God knows our frailty, [and] pities our weakness.
                                                  --Locke.
      [1913 Webster]

   2. A fault proceeding from weakness; foible; sin of
      infirmity.

   Syn: Frailness; fragility; imperfection; failing.
        [1913 Webster]

WordNet (r) 3.0 (2006):

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

Moby Thesaurus II by Grady Ward, 1.0:

147 Moby Thesaurus words for "frailty":
   abulia, airiness, airy texture, amiable weakness, attenuation,
   bad habit, besetting sin, blemish, breakability, breakableness,
   brittleness, bug, cachexia, cachexy, catch, changeableness,
   chronic ill health, collapse, cowardice, crack, crackability,
   crackableness, crispness, crumbliness, crushability, crushableness,
   daintiness, debilitation, debility, decrepitude, defect, defection,
   deficiency, delicacy, delicate health, destructibility,
   diaphanousness, dilutedness, dilution, disintegration, drawback,
   effeminacy, enervation, ethereality, exhaustion, exiguity, exility,
   failing, failure, faintheartedness, faintness, fallibility, fault,
   faute, fear, feeblemindedness, feebleness, fineness, fissility,
   flaw, flimsiness, foible, fracturableness, fragility, frangibility,
   friability, gauziness, gossameriness, gracility, healthlessness,
   hole, human equation, human frailty, human weakness, humanity,
   humanness, hypochondria, hypochondriasis, ill health, imperfection,
   impressionability, inadequacy, indecisiveness, infirmity,
   infirmity of will, inherent vice, insubstantiality, invalidism,
   invalidity, irresolution, kink, lacerability, laciness,
   languishing, languishment, liability, lightness, little problem,
   mistiness, moral flaw, moral weakness, morbidity, morbidness,
   mortality, paperiness, peakedness, pliability, poor health,
   problem, rarity, rift, shortcoming, sickliness, sleaziness,
   slenderness, slightness, slimness, snag, something missing,
   spinelessness, subtility, suggestibility, susceptibility, taint,
   tenuity, thinness, unhealthiness, unsoundness, unsubstantiality,
   unwholesomeness, vagueness, valetudinarianism, velleity, vice,
   vulnerability, vulnerable place, wasting, wateriness, weak link,
   weak point, weak side, weak will, weak-mindedness, weakliness,
   weakness, wispiness, womanishness