The Collaborative International Dictionary
irradiancy
irradiance \ir*ra"di*ance\ ([i^]r*r[=a]"d[i^]*ans), irradiancy \ir*ra"di*an*cy\ ([i^]r*r[=a]"d[i^]*an*s[y^]), n. [From irradiant.]
The act of irradiating; emission of rays of light.
That which irradiates or is irradiated; luster; splendor; irradiation; brilliancy.
--Milton.
Wiktionary
irradiancy
n. (alternative form of irradiance English)