A stipulative definition is a type of definition in which a new or currently existing term is given a new specific meaning for the purposes of argument or discussion in a given context. When the term already exists, this definition may, but does not necessarily, contradict the dictionary (lexical) definition of the term. Because of this, a stipulative definition cannot be "correct" or "incorrect"; it can only differ from other definitions, but it can be useful for its intended purpose.

For example, in the riddle of induction by Nelson Goodman, "grue" was stipulated to be "a property of an object that makes it appear green if observed before some future time t, and blue if observed afterward". "Grue" has no meaning in standard English; therefore, Goodman created the new term and gave it a stipulative definition.