From Longman Dictionary of Contemporary Englishmendaciousmen‧da‧cious /menˈdeɪʃəs/ adjective formal DISHONESTnot truthful mendacious propaganda —mendaciously adverb
Examples from the Corpus
mendacious• But Legasov's reassurance at Vienna was not as mendacious as many believed.• a secretive and mendacious government• If they carry on confounding chronology in this mendacious manner, they are likely to hit 30 as I reach 60.Origin mendacious (1600-1700) Latin mendax 