mendacious
- Not telling the truth; habitually lying or given to deception.
In a sentence
- The politician's mendacious campaign promises were exposed by journalists within months of his election.
- She grew weary of her mendacious colleague, who routinely took credit for other people's work.
Usage note. Mendacious refers to a habitual or characteristic tendency to lie, making it stronger than simply calling something 'untrue'; use it of persons or statements that reflect a pattern of deception.
Where it comes from
English mendacious · entered English mid-17th c.
From Latin 'mendax' (lying, deceitful), genitive 'mendacis', related to 'mendum' (fault, defect). The adjective form was built on the Latin stem and entered English in the mid-17th century, primarily in learned and legal contexts.