Very high energy electromagnetic radiation, like light or X-rays, but much higher in energy and frequency (and shorter in wavelength).
High-energy electromagnetic radiation emitted by certain radioactive nuclei. These rays have high energy and a short wave length. Stopping gamma rays requires thick layers of dense materials such as lead. Gamma rays are potentially lethal to humans depending on the dose.
(-rays) gamma radiation. A very high energy form of electromagnetic radiation, typically with wavelengths of less than 3 pm. Gamma rays are produced by certain nuclear decay processes, and are used to sterilize food.