The Collaborative International Dictionary of English v.0.48:

Hardiness \Har"di*ness\ (-d[i^]*n[e^]s), n.
   1. Capability of endurance.
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   2. Hardihood; boldness; firmness; assurance. --Spenser.
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            Plenty and peace breeds cowards; Hardness ever
            Of hardiness is mother.               --Shak.
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            They who were not yet grown to the hardiness of
            avowing the contempt of the king.     --Clarendon.
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   3. Hardship; fatigue. [Obs.] --Spenser.
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WordNet (r) 3.0 (2006):

hardiness
    n 1: the property of being strong and healthy in constitution
         [syn: robustness, hardiness, lustiness, validity]
    2: the trait of being willing to undertake things that involve
       risk or danger; "the proposal required great boldness"; "the
       plan required great hardiness of heart" [syn: boldness,
       daring, hardiness, hardihood] [ant: timidity,
       timorousness]