Definition of "irradiation"

An act of irradiating, or state of being irradiated.  examples

(obsolete) illumination; irradiance; brilliance.

(obsolete, figurative) mental light or illumination.

(obsolete) 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, especially when a little out of focus.

(uncountable) a process of sterilization whereby radiation is passed through a bag containing food, utensils, etc., to sterilize the contents.  examples