n. The act of injecting or throwing in; the act of forcing in, as a fluid into a passage, cavity, or substance of loose texture: as, the injection of a drug by means of a syringe; the injection of cold water into a steam-condenser to produce a vacuum.n. In anatomy, the act of injecting a body for dissection; the process of filling the vessels or other cavities of a body, or some part of a body, with a preservative, coloring, or other fluid.n. Specifically, in medicine, the giving of an enema; also, the enema given.n. That which is injected, as a fluid; specifically, any substance or preparation forced into an animal body to preserve it, display it, or otherwise fit it for dissection or other examination.n. The state of being hyperemic or bloodshot: as, the injection of the conjunctiva of an inflamed eye.n. Figuratively, a throwing in, as of a remark, hint, or suggestion; an injected saying or influence.n. In geology, the penetration of a rock by a molten magma.