irradiation /(ĭr*rā`dĭ*ā"shŭn)/

ir·ra·di·a·tion

irradiation

n.
  1. Act of irradiating, or state of being irradiated; as, irradiation of foods with X-rays can preserve their freshness by killing the bacteria that cause spoilage .
  2. Illumination; irradiance; brilliancy.
  3. Fig.: Mental light or illumination.
  4. 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. (Opt.)