The Collaborative International Dictionary of English v.0.48:

Gentility \Gen*til"i*ty\, n. [L. gentilitas the relationship of
   those who belong to the same clan, also, heathenism: cf. F.
   gentilit['e] heathenism. See Gentile.]
   [1913 Webster]
   1. Good extraction; dignity of birth. --Macaulay.
      [1913 Webster]

            He . . . mines my gentility with my education.
                                                  --Shak.
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   2. The quality or qualities appropriate to those who are well
      born, as self-respect, dignity, courage, courtesy,
      politeness of manner, a graceful and easy mien and
      behavior, etc.; good breeding.
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   3. The class in society who are, or are expected to be,
      genteel; the gentry. [R.] --Sir J. Davies.
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   4. Paganism; heathenism. [Obs.] --Hooker.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gentility
    n 1: elegance by virtue of fineness of manner and expression
         [syn: breeding, genteelness, gentility]

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "gentility":
   ancestry, appropriateness, aristocracy, aristocraticalness,
   becomingness, birth, blood, blue blood, breeding, civility,
   cultivation, culture, decency, decorousness, decorum, distinction,
   elegance, elite, felicity, fitness, fittingness, flower,
   genteelness, gentlemanlikeness, gentlemanliness, gentleness,
   gentry, good breeding, happiness, honorable descent, ladylikeness,
   meetness, nobility, noble birth, nobleness, polish, properness,
   propriety, quality, rank, refinement, rightness, royalty,
   seemliness, society, suitability, upper class, upper crust,
   urbanity