n. A joining; conjunction.n. In law: The coupling or joining of two causes of action in a suit against another: called more fully joinder of action.n. The coupling of two or more persons together as defendants.n. The acceptance by a party to an action of the point of controversy put in his adversary's previous pleading: called joinder in demurrer if the previous pleading was a demurrer, joinder of issue if it was an allegation of fact.