Nuclear weapon

Nuclear weapon is a device designed to release energy explosively from nuclear fission, nuclear fusion, or a combination of the two processes. Fission weapons are commonly referred to as atomic bombs. Fusion weapons are also referred to as thermonuclear bombs or, more commonly, hydrogen bombs; they are usually defined as nuclear weapons in which at least a portion of the energy is released by nuclear fusion. Nuclear weapons produce enormous explosive energy.
Their significance is appreciated by the coining of the words kiloton (1,000 tons) and
megaton (1,000,000 tons) to describe their blast energy in equivalent weights of the
conventional chemical explosive TNT[Encyclopedia Britannica].
A fully engineered assembly designed for employment to cause the release of a
chemical or biological agent or radiological material onto a chosen target or to
generate a nuclear detonation. Also called CBRN weapon (chemical, biological,
radiological, or nuclear weapon) [U. S. Department of Defense, p. 30].

Sources:

U. S. Department of Defense. (2017). Department of Defense Dictionary of Military and Associated Terms - As Amended Through 15 February 2016 - (Joint Publication 1-02). New York: Skyhorse.

Nuclear weapon. Encyclopedia Britannica. Retrieved from: https://www.britannica.com/technology/nuclear-weapon