A persuasive definition is a form of stipulative definition which purports to describe the true or commonly accepted meaning of a term, while in reality stipulating an uncommon or altered use, usually to support an argument for some view, or to create or alter rights, duties or crimes. The terms thus defined will often involve emotionally charged but imprecise notions, such as "freedom", "terrorism", "democracy", etc. In argumentation the use of a persuasive definition is sometimes called definist fallacy. (The latter sometimes more broadly refers to a fallacy of a definition based on improper identification of two distinct properties.)

Examples of persuasive definitions (definist fallacies) include:

• Democrat – "a leftist who desires to overtax the corporations and abolish freedom in the economic sphere".
• "Let's define atheist as someone who doesn't yet realize that God exists."

Persuasive definitions commonly 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. A persuasive definition of a term is favorable to one argument or unfavorable to the other argument, but is presented as if it were neutral and well-accepted, and the listener is expected to accept such a definition without question.

The term "persuasive definition" was introduced by philosopher Charles Stevenson as part of his emotive theory of meaning.