term:

Negative Averment

negative averment n

: a negative statement or allegation (as in a pleading) that constitutes a statement of fact and that must be proved by the party making it [a negative averment alleging that the plaintiff did not have the capacity to sue]

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.