I. noun — [ mass noun] 1. complete destruction or obliteration • the threat of global annihilation.
2. total defeat • a show of independence is its only hope of avoiding annihilation in next year’s elections.
[Physics] the conversion of matter into energy, especially the mutual conversion of a particle and an antiparticle into electromagnetic radiation.
– origin mid 16th cent.: from late Latin annihilatio(n-), from the verb annihilare (see annihilate).