The Collaborative International Dictionary of English v.0.48:

Propriety \Pro*pri"e*ty\, n.; pl. Proprieties. [F.
   propri['e]t['e], L. proprietas, fr. proprius one's own,
   proper. See Property, Proper.]
   1. Individual right to hold property; ownership by personal
      title; property. [Obs.] "Onles this propriety be exiled."
      --Robynson (More's Utopia).
      [1913 Webster]

            So are the proprieties of a wife to be disposed of
            by her lord, and yet all are for her provisions, it
            being a part of his need to refresh and supply hers.
                                                  --Jer. Taylor.
      [1913 Webster]

   2. That which is proper or peculiar; an inherent property or
      quality; peculiarity. [Obs.] --Bacon.
      [1913 Webster]

            We find no mention hereof in ancient zoographers, .
            . . who seldom forget proprieties of such a nature.
                                                  --Sir T.
                                                  Browne.
      [1913 Webster]

   3. The quality or state of being proper; suitableness to an
      acknowledged or correct standard or rule; consonance with
      established principles, rules, or customs; fitness;
      appropriateness; as, propriety of behavior, language,
      manners, etc. "The rule of propriety," --Locke.
      [1913 Webster]

WordNet (r) 3.0 (2006):

propriety
    n 1: correct or appropriate behavior [syn: propriety,
         properness, correctitude] [ant: improperness,
         impropriety]

Moby Thesaurus II by Grady Ward, 1.0:

179 Moby Thesaurus words for "propriety":
   Atticism, admissibility, advantage, advantageousness, advisability,
   amenities, applicability, appositeness, appropriateness, aptitude,
   aptness, auspiciousness, becomingness, beneficialness, bienseance,
   breeding, ceremony, chargedness, chasteness, chastity, civilities,
   civility, clarity, classicalism, classicism, clearness, comeliness,
   conformity, convenance, convenience, convention,
   conventional usage, conventionalism, conventionality, correctitude,
   correctness, courtesy, criticality, crucialness, custom, decencies,
   decency, decorousness, decorum, defensibility, delicacy,
   desirability, dignity, directness, discrimination, distinction,
   drumhead justice, dueness, ease, elegance, elegancy, equitableness,
   equity, etiquette, evenhandedness, expedience, expediency,
   favorableness, feasibility, felicitousness, felicity, finish,
   fitness, fittedness, fittingness, flow, flowing periods, fluency,
   form, formality, fruitfulness, genteelness, gentility,
   give-and-take, good form, good taste, goodness, grace,
   gracefulness, gracility, happiness, health, justice,
   justifiability, justifiableness, justification, justness,
   lawfulness, legality, limpidity, loadedness, lucidity,
   mannerliness, measure for measure, meetness, modesty, mores,
   naturalism, naturalness, naturism, neatness, nemesis, niceness,
   normalcy, normality, normalness, normativeness, opportuneness,
   order, orderliness, pellucidity, percentage, perspicuity,
   plainness, poetic justice, polish, politeness, politesse,
   politicness, pregnancy, profit, profitability, properness,
   propitiousness, proprieties, protocol, prudence, pudency, pudicity,
   punctilio, purity, qualification, realism, refinement, regularity,
   relevance, respectability, restraint, retributive justice, right,
   righteousness, rightfulness, rightness, ripeness, ritual,
   rude justice, scales of justice, seasonableness, sedateness,
   seemliness, shame, simplicity, smoothness, social convention,
   social usage, straightforwardness, suitability, suitableness,
   summary justice, taste, tastefulness, terseness, the proprieties,
   timeliness, tradition, unaffectedness, urbanity, usefulness,
   warrantability, warrantedness, what is right, wholesomeness,
   wisdom, worthwhileness