0. Global radiation is the total short-wave radiation from the sky falling onto a horizontal surface on the ground. It includes both the direct solar radiation and the diffuse radiation resulting from reflected or scattered sunlight.
1. the process in which energy is emitted as particles or waves.
2. The complete process in which energy is emitted by one body, transmitted through intervening medium or Space, and absorbed by an other body.
https://www.pik-potsdam.de/services/climate-weather-potsdam/climate-diagrams/global-radiation (0.); http://www.thesaurus.com/browse/radiation. (1.); http://www.freethesaurus.com/radiative. (2.)