say it: ir-ay-dee-AY-shuhn
irradiation is a noun meaning "the condition of being exposed to radiation". It carries 6 recorded senses.
the condition of being exposed to radiation
a column of light (as from a beacon)
the apparent enlargement of a bright object when viewed against a dark background
(Pavolvian conditioning) the elicitation of a conditioned response by stimulation similar but not identical to the original stimulus
(medicine) the treatment of disease (especially cancer) by exposure to a radioactive substance
medicine
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for irradiation come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.