a process whereby a gamma ray having an energy greater than 1.02 MeV is converted into an electron and positron pair in the strong electric field of a nucleus
See pair production in American Heritage Dictionary 4
noun
The simultaneous creation of a subatomic particle and its antiparticle from another form of energy, especially the production of a positron and an electron from a gamma ray photon in a strong electric field, such as that surrounding a nucleus.