(physics) A nucleus of an atom; consisting of protons and neutrons, surrounded by an electron cloud.

(physics) an early nuclear reactor fuelled by uranium and moderated with graphite

The era, starting in the mid-1940s, during which nuclear energy was developed, and in which it was thought that all energy would be provided by such sources.

(physics, chemistry) the equivalent of an atom in which either the nucleus, or an electron, is replaced by some other subatomic particle

(physics) any device that converts the energy of particles emitted from atomic nuclei into electrical energy

(physics, chemistry) Any atom which has a single valence electron in a shell well outside any other electrons in the aton; approximates the hydrogen atom.

Alternative letter-case form of Atomic Age

(philosophy) The doctrine that the world consists of ultimate logical "facts" (or "atoms") that cannot be broken down any further.

(informal) A particle accelerator.

(physics) Synonym of nuclear fission