gamma-ray burst

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A short-lived, localized, and intense burst of gamma radiation that originates outside the solar system.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun astronomy A flash of gamma rays that seem to originate from a random point in the sky; their most likely sources are believed to be supernova explosions of a very massive stars and mergers of neutron stars.