Spontaneous emission of ionizing radiation as a consequence of a nuclear reaction, or directly from the breakdown of an unstable nucleus.

Exhibiting radioactivity. / (figuratively, rare) Dangerous and disgusting, particularly of people or ideas.

Any radioactive substance.

Using a radioactive substance / Concerning radioactivity

plural of radioactive

plural of radioactivity

(physics, chemistry, medicine) A radioactive isotope which, when injected into a chemically similar substance, or artificially attached to a biological or physical system, can be traced by radiation detection devices.

material settling from a radioactive plume, and its subsequent surface deposition

Waste containing radioactive nuclides.

(physics) Any of several processes by which unstable nuclei emit subatomic particles and/or ionizing radiation and disintegrate into one or more smaller nuclei.