annihilation: Meaning and Definition of

an•ni•hi•la•tion

1. the act or an instance of annihilating.
2. the state of being annihilated; extinction; destruction.
1. Also calledpair annihilation.the process in which a particle and antiparticle unite, annihilate each other, and produce one or more photons. Cf. positronium.
2. the conversion of rest mass into energy in the form of electromagnetic radiation.