act of irradiating, or state of being irradiated.-illumination; irradiance; brilliancy.-fig.: mental light or illumination.-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.