Pronunciation: (i-rā"dē-ā'shun), [key]
1. the act of irradiating.
2. the state of being irradiated.
3. intellectual or spiritual enlightenment.
4. a ray of light; beam.
5. Optics.the apparent enlargement of an object when seen against a dark background.
6. the use of x-rays or other forms of radiation for the treatment of disease, the making of x-ray photographs, the manufacture of vitamin D, etc.
7. exposure or the process of exposure to x-rays or other radiation.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.