A weapon of mass destruction is a nuclear, radiological, chemical, biological, or any 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 use of such weapons in war is featured.

Notes:
We consider that the mere existence of a WMD implies its potential use in war as these devices really have no other credible purpose.

Examples:
Biological, chemical, and nuclear weapons are commonly found beneath the moniker "weapons of mass destruction".

References:
https://en.wikipedia.org/wiki/Weapon_of_mass_destruction