CURRENT USAGE: "These [UN] reports do not contend that weapons of mass destruction remain in Iraq, but nor do they exclude that possibility." Dr Hans Blix's statement to the UN Security Council - 27/01/03.

ORIGIN: British newspapers called bomber aircraft "weapons of mass destruction" in 1937, when the Nazi Luftwaffe was flattening towns - such as Guernica - during the Spanish Civil War.

In the arms race of the Cold War, WMD was exclusively applied to thermo-nuclear bombs - since the opposing sides were ready with enough nukes to mutually assure the destruction of, well, everything.

BROADENED DEFINITION: UN Resolution 687 - which ended the Gulf War in 1991 - called on Iraq to relinquish its NBC ambitions and summed up the unpleasant trio as WMD.

In 1998, US law formalised WMD as devices able "to cause death or serious bodily injury to a significant number of people" using chemicals, a disease organism, radiation or radioactivity.

DISPUTED DEFINITION: the FBI says conventional explosives can also be WMD. "A weapon crosses the WMD threshold when the consequences of its release overwhelm local responders."

DISPUTED DEFINITION (TWO): Colombia's Vice President Gustavo Bell Lemus told the UN that small arms are also WMD, because bullet fatalities "dwarf that of all other weapons systems - and in most years greatly exceed the toll of the atomic bombs that devastated Hiroshima and Nagasaki".

DISPUTED DEFINITION (THREE): some say that fewer - rather than more - weapons should be deemed capable of mass destruction.

"Only nuclear weapons are completely indiscriminate by their explosive power, heat radiation and radioactivity, and only they should therefore be called a weapon of mass destruction" says chemical weapons expert Gert G Harigel.

ALTERNATIVES: Mr Harigel prefers to call clouds of anthrax or poison gas or radioactive dust "weapons of terror" when aimed against civilians and "weapons of intimidation" for soldiers in gas masks and protective suits.

"Weapons of indiscriminate destruction", "weapons of mass disruption" and "weapons of catastrophic effect" have also been suggested.

MASS USE: WMD has had a mass impact of its own. Its recent ubiquity has earned it a place on Lake Superior State University's famed list of "misused, overused and generally uselessness" words.