irradiation
Concise Oxford English Dictionary © 2008 Oxford University Press:
irradiation/ɪreɪdiˈeɪʃn/
▶noun
- 1 the process or fact of irradiating or being irradiated.
- 2 Optics the apparent extension of the edges of an illuminated object seen against a dark background.
'irradiation' also found in these Oxford entries:

