The term "weapons of mass destruction" has been around for decades, but it's become much more common in recent years, particularly since the run-up to the war in Iraq. (The American Dialect Society chose the phrase, and its abbreviation, WMD, as the 2002 Word of the Year.)

In the Iraq debate, "weapons of mass destruction" was generally used as a catchall term for nuclear, chemical, and biological weapons. But on Tuesday, when federal authorities submitted their five-count complaint against Faisal Shahzad, the man they say tried to detonate an explosive-laden SUV in Times Square this weekend, the top charge was that he attempted to use weapons of mass destruction.*

Shazad is just the latest terror suspect to face that WMD charge. Umar Farouk Abdulmutallab, the Nigerian man accused of trying to detonate plastic explosives hidden in his underwear on a Northwest Airlines flight last Christmas Day, was also indicted on the WMD charge. And in February, Najibullah Zazi pleaded guilty to conspiracy to use weapons of mass destruction, among other charges, for his role in a plot to set off explosives, made with beauty supply chemicals, in New York subways.

So is a Pathfinder loaded with explosives -- or a pair of underwear with a bomb in them -- a weapon of mass destruction?

Each can be, according to the U.S. criminal code.

The section of the law referenced in the complaint defines a “weapon of mass destruction” much more broadly than common use did in the case of Saddam Hussein. It includes radiological, chemical, and biological weapons. But besides those categories, the law also defines a weapon of mass destruction as a “destructive device,” another broad term that, according to its legal definition, can include a bomb, grenade, rocket, missile, mine, or other device with a charge of more than four ounces.

Here's the definition of the term "destructive device" as laid out in Title 18, United States Code, Section 921:

(A) any explosive, incendiary, or poison gas --

(i) bomb,

(ii) grenade,

(iii) rocket having a propellant charge of more than four ounces,

(iv) missile having an explosive or incendiary charge of more than one-quarter ounce,

(v) mine, or

(vi) device similar to any of the devices described in the preceding clauses;

(B) any type of weapon (other than a shotgun or shotgun shell which the Attorney General finds is generally recognized as particularly suitable for sporting purposes) by whatever name known which will, or which may be readily converted to, expel a projectile by the action of an explosive or other propellant, and which has any barrel with a bore of more than one-half inch in diameter; and

(C) any combination of parts either designed or intended for use in converting any device into any destructive device described in subparagraph (A) or (B) and from which a destructive device may be readily assembled.

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* The court filing, in splendorous legal jargon, says Shahzad "unlawfully, willfully, and knowingly, and without lawful authority, did attempt to use a weapon of mass destruction, namely, a destructive device as defined by Title 18, United States Code, Section 921, against persons and property within the United States, to wit, on or about May 1, 2010, Shahzad traveled from Connecticut to New York and attempted to detonate improvised explosive and incendiary devices inside a sports utility vehicle located in the vicinity of 45th Street and Seventh Avenue in Manhattan, New York.”