Read the dictionary definition of irradiation. All definitions for this word.
1. (medicine) the treatment of disease (especially cancer) by exposure to a radioactive substance
2. (Pavolvian conditioning) the elicitation of a conditioned response by stimulation similar but not identical to the original stimulus
3. the apparent enlargement of a bright object when viewed against a dark background
4. (physiology) the spread of sensory neural impulses in the cortex
5. a column of light (as from a beacon)
6. the condition of being exposed to radiation