MENDACIOUS Meaning of MENDACIOUS in English [ mɛn'deɪʃəs ]■ adjective untruthful: ~ propaganda. Derivatives~ly adverbmendacity noun OriginC17: from L. mendax , mendac- 'lying' + -ious . Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004