Meaning of annihilation radiation

annihila'tion radia"tion

Pronunciation: [key]
— Physics. Physics.
  1. electromagnetic radiation produced by the coalescence and mutual annihilation of a positron and an electron, each pair forming two photons having a minimum energy of 0.5 million electron volts each.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.