Source : Webster's Revised Unabridged Dictionary (1913)

Mendacious \Men*da"cious\, a. [L. mendax, -acis, lying, cf.
   mentiri to lie.]
   1. Given to deception or falsehood; lying; as, a mendacious
      person.

   2. False; counterfeit; containing falsehood; as, a mendacious
      statement. -- {Men*da"cious*ly}, adv. --
      {Men*da"cious*ness}, n.

Source : WordNet®

mendacious
     adj 1: given to lying; "a lying witness"; "a mendacious child"
            [syn: {lying(a)}]
     2: intentionally untrue; "a mendacious statement"