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