Available Definitions:
1) n. - Act of irradiating, or state of being irradiated.
2) n. - Illumination; irradiance; brilliancy.
3) n. - Fig.: Mental light or illumination.
4) n. - 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.