<p><strong>Noun</strong></p><ul><li>an act or instance of annihilating, or of completely destroying or defeating someone or something: the brutal annihilation of millions of people.</li><li>the state of being annihilated; total destruction; extinction: fear of nuclear annihilation.</li><li>(Physics) Also called pair annihilation: the process in which a particle and antiparticle unite, annihilate each other, and produce one or more photons.</li><li>the conversion of rest mass into energy in the form of electromagnetic radiation.</li></ul>