The simplest definition for "mendacious" is untruthful. The word mendacious is used to refer to several types of communications or omissions that serve to distort or omit the complete truth. Most people expect friends, relational partners, and even strangers to be truthful most of the time. A mendacious person is one who tells lies habitually and intentionally. People may tell "white lies" if they forgot your birthday or really don't like your new haircut, but if you catch someone intentionally manipulating you with a falsehood, that person is just plain mendacious. The most deceptive, insincere, perfidious, duplicitous or false person you've ever met is also mendacious. He or she is given to lying (untruthfulness).

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