The conspiracy theories for Weapons of Mass Destruction are vast and numerous. From theories suggesting that George W. Bush intentionally misled the US about weapons of mass destruction in Iraq. Just so they could have a reason to invade. All the way to some lesser known theories that suggest Nuclear Weapons just dont exist to begin with.
A weapon of mass destruction (WMD or WoMD) is a nuclear, radiological, chemical, biological or other weapon that can kill and bring significant harm to a large number of humans or cause great damage to human-made structures (e.g. buildings), natural structures (e.g. mountains), or the biosphere. The scope and application of the term has evolved and been disputed, often signifying more politically than technically. Coined in reference to aerial bombing with chemical explosives, it has come to distinguish large-scale weaponry of other technologies, such as chemical, biological, radiological, or nuclear. This differentiates the term from more technical ones such as chemical, biological, radiological, and nuclear weapons (CBRN). - Source: Wikipedia