Spurious radiation at frequencies resulting from intermodulation between the oscillation and the carrier, characteristic or harmonic frequencies of an emission, or the oscillations which appear when this carrier or characteristic oscillations are produced, and oscillations of the same nature of the same or several other emissions originating from the same or different transmitting systems.
Reference: C.C.I.R. (modified)
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