noun fig.: mental light or illumination.
2. irradiation ·noun illumination; irradiance; brilliancy.
3. irradiation ·noun act of irradiating, or state of being irradiated.
4. irradiation ·noun 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.