The Collaborative International Dictionary of English v.0.48:

Virtuous \Vir"tu*ous\ (?; 135), a. [OE. vertuous, OF. vertuos,
   vertuous, F. vertueux, fr. L. Virtuous. See Virtue, and cf.
   Virtuoso.]
   1. Possessing or exhibiting virtue. Specifically:
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      (a) Exhibiting manly courage and strength; valorous;
          valiant; brave. [Obs.]
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                Old Priam's son, amongst them all, was chiefly
                virtuous.                         --Chapman.
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      (b) Having power or efficacy; powerfully operative;
          efficacious; potent. [Obs.] --Chaucer.
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                Lifting up his virtuous staff on high,
                He smote the sea, which calm['e]d was with
                speed.                            --Spenser.
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                Every virtuous plant and healing herb. --Milton.
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      (c) Having moral excellence; characterized by morality;
          upright; righteous; pure; as, a virtuous action.
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                The virtuous mind that ever walks attended
                By a strong siding champion, conscience.
                                                  --Milton.
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   2. Chaste; pure; -- applied especially to women.
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            Mistress Ford . . . the virtuous creature, that hath
            the jealous fool to her husband.      --Shak.
      [1913 Webster] -- Vir"tu*ous*ly, adv. --
      Vir"tu*ous*ness, n.
      [1913 Webster] Virulence

WordNet (r) 3.0 (2006):

virtuousness
    n 1: the quality of doing what is right and avoiding what is
         wrong [syn: virtue, virtuousness, moral excellence]