annihilation

an·ni·hi·la·tion | \ ə-ˌnī-ə-ˈlā-shən

plural annihilations

Definition of annihilation

1 : the state or fact of being completely destroyed or obliterated : the act of annihilating something or the state of being annihilated The late 1940s and '50s were so pervaded by a general fear of nuclear annihilation that the era was known as the Age of Anxiety.— Charles Krauthammer For a literary culture that fears it is on the brink of total annihilation, we are awfully cavalier about the Great Male Novelists of the last century.— Katie Roiphe … few experts believe that either regime would risk annihilation by actually launching a nuke in anger.— Michael Elliott The Cretaceous Extinction, whatever its cause, was one of the two most awesome annihilations of life in the history of the world.— John McPhee

2 physics : the combination of a particle and its antiparticle (such as an electron and a positron) that results in the subsequent total conversion of the particles into energy Both the creation and annihilation of antimatter have been observed in nuclear accelerators (atom-smashers).— Harding E. Smith The annihilation reactions are the most efficient sources of energy known, for in them the entire mass of both particles is converted into pure energy.— George Greenstein