1. An act or process of causing water to flow by mechanical distribution; usually, on agricultural land with ditches, or artificial canals, etc.: "Farmers in dry areas use irrigation to grow food crops."
2. A medical system of washing out a part of the body; such as, a cavity or a wound in order to clean it for further medical treatment: "One example is colonic irrigation and another one is the irrigation of an open wound before the doctor proceeds with additional treatments."