Source : Webster's Revised Unabridged Dictionary (1913)

Propensity \Pro*pen"si*ty\, n.; pl. {Propensities}.
   The quality or state of being propense; natural inclination;
   disposition to do good or evil; bias; bent; tendency. ``A
   propensity to utter blasphemy.'' --Macaulay.

   Syn: Disposition; bias; inclination; proclivity; proneness;
        bent; tendency.