The Collaborative International Dictionary of English v.0.48:

Modesty \Mod"es*ty\, n. [L. modestia: cf. F. modestie. See
   Modest.]
   1. The quality or state of being modest; that lowly temper
      which accompanies a moderate estimate of one's own worth
      and importance; absence of self-assertion, arrogance, and
      presumption; humility respecting one's own merit.
      [1913 Webster]

   2. Natural delicacy or shame regarding personal charms and
      the sexual relation; purity of thought and manners; due
      regard for propriety in speech or action.
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            Her blush is guiltiness, not modesty. --Shak.
      [1913 Webster]

   Modesty piece, a narrow piece of lace worn by women over
      the bosom. [Obs.] --Addison.
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   Syn: Bashfulness; humility; diffidence; shyness. See
        Bashfulness, and Humility.
        [1913 Webster]

WordNet (r) 3.0 (2006):

modesty
    n 1: freedom from vanity or conceit [syn: modesty,
         modestness] [ant: immodesty]
    2: formality and propriety of manner [syn: modesty, reserve]