Source : Webster's Revised Unabridged Dictionary (1913)

Mendacity \Men*dac"i*ty\, n.; pl. {Mendacities}. [L.
   mendacitas.]
   1. The quality or state of being mendacious; a habit of
      lying. --Macaulay.

   2. A falsehood; a lie. --Sir T. Browne.

   Syn: Lying; deceit; untruth; falsehood.

Source : WordNet®

mendacity
     n : the tendency to be untruthful [ant: {veracity}]