Process of emission in which the radiant energy originates in the thermal agitation of the particles of matter (atoms, molecules, ions).
Note: The terms "thermal radiation" and, in German Temperaturstrahlung apply not only to the process of emission, but also to the radiation itself.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
Celsius (previously Centigrade)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM