Definitions for "Gamma ray"
A very penetrating electromagnetic ray not appreciably deflected by a magnetic or electric field, emitted by radioactive substances. Gamma rays are photons of electromagnetic radiation having a wavelength shorter than that of X-rays, (i. e. shorter than 0.1 nanometer) and are correspondingly more penetrating than X-rays. In addition to being given off in certain types of radioactive decay, they may be found in cosmic radiation, though they are largely absorbed by the earth's atmosphere. Gamma-ray detectors orbited above the atmosphere have found bursts of gamma radiation, in some cases associated with visually observed supernova explosions, but in most cases from unidentified sources.
high-energy electromagnetic particle or photon, especially as emitted by a nucleus in its transition from one energy level to another. Radiation whose wavelength is less than one Angstrom is usually considered to be gamma-ray radiation.
A high-energy, short wavelength form of electromagnetic radiation emitted by the nucleus of an atom that carries off some of the energy released in a nuclear reaction.