A weapon of mass destruction (WMD) is a weapon that can kill large numbers of humans and/or cause great damage to man-made structures (e.g. buildings), natural structures (e.g. mountains), or the biosphere in general.
The term is often used to cover several weapon types, including nuclear, biological, chemical (NBC) and radiological weapons. Additional terms used in a military context include atomic, biological, and chemical warfare (ABC) and chemical, biological, radiological, and nuclear (CBRN) warfare.
The phrase was predominantly used in reference to nuclear weapons during the Cold War; following the collapse of the Soviet Union and increasing tensions between the Middle East and the Western powers, the term broadened to its modern, more inclusive definition. It entered widespread usage in relation to the U.S.-led 2003 invasion of Iraq.