Joinder in demurrer
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
When a defendant in an action tenders an issue of law, (called a "demurrer,") the plaintiff, if he means to maintain his action, must accept it, and this acceptance of the defendant's tender, signified by the plaintiff in a set form of words, is calied a "joinder in demurrer."
Brown.