atom bomb or atomic bomb noun

A nuclear device in which quantities of uranium-235 or plutonium are forced to become critical with the result that their nuclei are bombarded by neutrons and split with explosive transformation of part of their mass into energy

atomic clock noun

A clock in which, to achieve greater accuracy, the oscillations of a quartz crystal (qv) are regulated by the vibration of certain atoms such as a caesium atom

atomic energy noun

Nuclear energy

atomic mass unit noun

1/12 of the mass of an atom of carbon-12

atomic number noun

The number of units of charge of positive electricity on the nucleus of an atom of an element

atomic philosophy noun

A system of philosophy enunciated by Democritus, which taught that the ultimate constituents of all things are indivisible particles, differing in form and in their relations to each other

atomic pile noun

An early name for a device for the controlled release of nuclear energy, eg a lattice of small rods of natural uranium embedded in a mass of pure graphite which serves to slow down neutrons

atomic power, atomic radiator see atomic above.

atomic second noun

A time interval whose measurement uses the frequency of radiation emitted or absorbed during transition from one energy state to another of a chosen atom

atomic theory noun

The hypothesis that all atoms of the same element are alike and that a compound is formed by union of atoms of different elements in some simple ratio

atomic time noun

Time whose unit is the atomic second

atomic transmutation noun

The change of one type of atom to another as a result of a nuclear reaction

atomic volume noun

The atomic weight of an element divided by its density

atomic warfare noun

Warfare using atomic weapons

atomic weight noun

Relative atomic mass (qv under relate)

aˈtom-smasher noun (informal)

An apparatus for breaking up the atom, an accelerator

Atomic Energy Authority and Atomic Energy Commission

The respective bodies in Britain and the USA responsible for the development and control of atomic energy

primeval atom

A hypothetical dense conglomerate from whose explosion 60 thousand million years ago the universe was (according to one theory) gradually formed