mendaciously

This term carries a heavy, formal register and is rarely used in casual conversation. It suggests not just a single lie, but a deliberate, calculated, or habitual pattern of deception. Because of its Latinate origin, it is most frequently encountered in legal documents, academic critiques, or high-style literature to describe a character's dishonesty.

Compared to "dishonestly," which is a broad term for any lack of integrity, "mendaciously" specifically targets the act of lying. While "dishonestly" could refer to stealing or cheating without speaking, "mendaciously" almost always involves the communication of false information.