Definition of "Irradiation" :

noun: (medicine) the treatment of disease (especially cancer) by exposure to a radioactive substance

noun: (Pavolvian conditioning) the elicitation of a conditioned response by stimulation similar but not identical to the original stimulus

noun: the apparent enlargement of a bright object when viewed against a dark background

noun: (physiology) the spread of sensory neural impulses in the cortex

noun: a column of light (as from a beacon)

noun: the condition of being exposed to radiation