Definify.com
Webster 1913 Edition
irradiation
ir-raˊdi-a′tion
(ĭr-rāˊdĭ-ā′shŭn)
, Noun.
[Cf. F.
irradiation
.] 2.
Illumination; irradiance; brilliancy.
Sir W. Scott.
3.
Fig.: Mental light or illumination.
Sir M. Hale.
4.
(Opt.)
The apparent enlargement of a bright object seen upon a dark ground, due to the fact that the portions of the retina around the image are stimulated by the intense light; as when a dark spot on a white ground appears smaller, or a white spot on a dark ground larger, than it really is, esp. when a little out of focus.
Webster 1828 Edition
Irradiation
IRRADIA'TION
,Noun.
1.
Illumination; brightness.2.
Intellectual light.3.
The act of emitting minute particles or effluvia from some substance.