D defs.my
Entry 4 senses Webster, 1913

irradiation

/(ĭr*rā`dĭ*ā"shŭn)/ · ir·ra·di·a·tion · IPA /ɪˌɹeɪdiˈeɪʃən/
01 n. Act of irradiating, or state of being irradiated; as, irradiation of foods with X-rays can preserve their freshness by killing the bacteria…
  1. 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. 2.
    Illumination; irradiance; brilliancy.
  3. 3.
    Fig.: Mental light or illumination.
  4. 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.)