natural philosophy, physical science, physics - the science of matter and energy and their interactions

chain reaction - a self-sustaining nuclear reaction; a series of nuclear fissions in which neutrons released by splitting one atom leads to the splitting of others

radioactive decay, disintegration, decay - the spontaneous disintegration of a radioactive substance along with the emission of ionizing radiation

endoergic reaction - a nuclear reaction occurring with absorption of energy

exoergic reaction - a nuclear reaction accompanied by the evolution of energy

fission, nuclear fission - a nuclear reaction in which a massive nucleus splits into smaller nuclei with the simultaneous release of energy

nuclear fusion, nuclear fusion reaction, fusion - a nuclear reaction in which nuclei combine to form more massive nuclei with the simultaneous release of energy

natural action, natural process, activity, action - a process existing in or produced by nature (rather than by the intent of human beings); "the action of natural forces"; "volcanic activity"

spallation - (physics) a nuclear reaction in which a bombarded nucleus breaks up into many particles; "some astronomers believe that the solar system was formed by spallation when the sun was a very young star"