Negative averment
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
As opposed to the traverse or simple denial of an affirmative allegation, a negative averment is an allegation of some substantive fact, e. g., that premises are not in repair, which, although negative in form, is really affirmative in substance, and the party alleging the fact of non-repair must prove t.
Brown.