1.Act of irradiating, or state of being irradiated; as, irradiation of foods with X-rays can preserve their freshness by killing the bacteria that cause spoilage .
2.Illumination; irradiance; brilliancy.
3.Fig.: Mental light or illumination.
4.(Opt.) The apparent enlargement of a bright object seen upon a dark ground, due to the fact that the portions of the retina around the image are stimulated by the intense light; as when a dark spot on a white ground appears smaller, or a white spot on a dark ground larger, than it really is, esp. when a little out of focus.
