The Collaborative International Dictionary of English v.0.48:

Mendacity \Men*dac"i*ty\, n.; pl. Mendacities. [L.
   mendacitas.]
   1. The quality or state of being mendacious; a habit of
      lying. --Macaulay.
      [1913 Webster]

   2. A falsehood; a lie. --Sir T. Browne.
      [1913 Webster]

   Syn: Lying; deceit; untruth; falsehood.
        [1913 Webster]

WordNet (r) 3.0 (2006):

mendacity
    n 1: the tendency to be untruthful [ant: veracity]

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "mendacity":
   blague, boggling, caviling, cock-and-bull story, credibility gap,
   dishonesty, dodging, equivocation, exaggeration, fairy tale,
   falsehood, falsity, farfetched story, farrago, fib, fibbery,
   fibbing, fiction, fish story, flam, flimflam, ghost story,
   half-truth, hedging, legal fiction, lie, little white lie, lying,
   mendaciousness, mythomania, pious fiction, prevarication,
   pseudology, quibbling, shifting, sidestepping, slight stretching,
   story, tale, tall story, tall tale, taradiddle, trumped-up story,
   truthlessness, untruth, untruthfulness, unveraciousness, white lie,
   yarn