Duplicity means dishonest talk or behavior, especially involving saying different things to different people or acting in a way that hides one's true intentions. It is essentially double-dealing or deceitfulness aimed at misleading others. The term can also broadly mean contradictory doubleness of thought, speech, or action, with an emphasis on deception by pretending one thing while acting with another intention.

In a formal context, duplicity refers to dishonest behavior intended to trick someone. For example, a person might say one thing but mean something entirely different, thereby deceiving others.

There is also a legal meaning of duplicity, which is a technical error where a single indictment charge improperly covers more than one offense, but the most common use is about deceitful behavior or double-dealing in everyday language.