Attempted use of a weapon of mass destruction

Perplexed by the fact that the fact that Umar Farouk Abdulmutallab the Nigerian terrorist is being indicted on a charge of "attempted use of a weapon of mass destruction", I went to check the definitions of WMDs by U.S. Penal code and here is what I found :

§ 2332a. Use of weapons of mass destruction.
(c) Definitions.— For purposes of this section—
(2) the term “weapon of mass destruction” means—
(A) any destructive device as defined in section 921 of this title;
(B) any weapon that is designed or intended to cause death or serious bodily injury through the release, dissemination, or impact of toxic or poisonous chemicals, or their precursors;
(C) any weapon involving a biological agent, toxin, or vector (as those terms are defined in section 178 of this title); or
(D) any weapon that is designed to release radiation or radioactivity at a level dangerous to human life.

Intrigued I looked up the definition of destructive device.

(4) The term “destructive device” means—
(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;

I would have never thought the definition of something that is applied usually to nuclear bombs, can be applied to land mines, (well one thing is for sure by these definitions G.W.Bush was right about Iraq)

If you had the patience to read all this, thank you.