n. The act of infusing, pouring in, imbuing, or instilling: as, the infusion of good principles.n. That which is infused or diffused; something poured in or mingled.n. The process of steeping a substance, as a plant, in water, in order to extract its virtues.n. A liquid extract or essence obtained by steeping a vegetable substance.n. A pouring, or pouring out, as upon an object; affusion: formerly used of that method of baptism in which the water is poured upon the person.n. The introduction into a vein of a quantity of saline solution or other fluid for therapeutic purposes.