D defs.my
Entry 2 senses Webster, 1913

Radiation

/(rā`dĭ*ā"shŭn)/ · Ra·di·a·tion · IPA /ˌɹeɪ.diˈeɪ.ʃən/
01 n. The act of radiating, or the state of being radiated; emission and diffusion of rays of light; beamy brightness.
  1. 1.
    The act of radiating, or the state of being radiated; emission and diffusion of rays of light; beamy brightness.
  2. 2.
    The shooting forth of anything from a point or surface, like the diverging rays of light; as, the radiation of heat.