An extremely accurate reference clock whose operation is based on an atomic process, typically the frequency of electromagnetic radiation associated with a specified energy-level transition in an element such as cesium.

Alternative form of atomic bomb

(physics) The theory that all gross matter is composed of atoms. / (physics) Any of several theories that explain the structure of the atom, and of subatomic particles.

Alternative spelling of subatomic

Alternative spelling of subatomic

A nuclear weapon.

(uncommon) Nuclear winter.

(physics) a hydrogen-like system consisting of an ordinary nucleus with a hadron in orbit.

(quantum mechanics, chemistry) A mathematical function that describes the wave-like behavior of either one electron or a pair of electrons in an atom. This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus.

(countable, military) A nuclear weapon that obtains its destructive energy from nuclear fission.