A persuasive definition is a type of definition in which a term is defined in such a way as to be an argument for a particular position (as opposed to a lexical definition, which aims to be neutral to all usages), and is deceptive in that it has the surface form of a dictionary definition. As such, when a definition is recognized as persuasive, it is not accepted as legitimate, and often considered fallacious. Persuasive definitions are put forth not as a legitimate attempt to define, but rather to make a point about the viewpoint expressed.

For example, Ambrose Bierce, in The Devil's Dictionary, defines "heathen" as "a benighted creature who has the folly to worship something that he can see and feel." The lexical definition would usually be along the lines of "one who does not believe in the Christian God" or "one who does not follow an established religion". Bierce's definition attempts to make the case for the heathen's position (by using irony), suggesting that it is foolish to believe in something you cannot see or feel. This definition would be inappropriate for theological argument, as it is biased toward one side.

Persuasive definitions appear in controversial topics such as politics, sex, and religion, as participants in emotionally-charged exchanges will sometimes become more concerned about swaying people to one side or another than expressing the unbiased facts.