1. The act of exposing or the condition of being exposed to radiation.
2. The use or application of ionizing radiation, especially in medical treatment and for the sterilization or preservation of food.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.