A less commonly used phrase with essentially the same meaning as "nuclear, biological, chemical (NBC) weapon." This phrase is probably more technically correct because dirty bombs are not truly nuclear weapons, but rather radiological weapons. Nevertheless, dirty bombs are considered one of the NBC perils that insurers typically seek to exclude in the commercial lines policies they write.

Chemical, biological, radiological, and nuclear weapons that cause damage, destroy, or contaminate an extraordinarily wide area or inflict wide-scale sickness, death, or injury.

Weapons that disperse biological, chemical, or radioactive agents to inflict injury or cause contamination or damage. A dirty bomb using a conventional explosion to disperse radioactive contaminants would be included under the first category, as would a nuclear device that relies on nuclear fission to generate an explosion. Examples of biological agents would include anthrax and smallpox. Examples of chemical agents would include mustard gas, ricin, VX, and sarin gas. Due to the truly catastrophic exposure they pose, insurers generally exclude coverage for NBC perils—or seek a substantially higher premium to cover them—even when covering other acts of terrorism.

A device utilizing conventional explosive materials, such as TNT or dynamite, to disperse radioactive material over a wide area, thereby contaminating the area. This is in contrast to a nuclear weapon, which relies on a nuclear-fission reaction to generate an extremely powerful explosive blast (although the term was originally coined for nuclear weapons that caused excessive contamination). The destructiveness of a dirty bomb would depend primarily upon the force of the conventional explosion. However, the resulting radioactive contamination would potentially make the area useless, or at the least cause people to panic. Manufacturing a dirty bomb is not significantly more complex than manufacturing a conventional bomb, and many types of radioactive materials could be used. Weapons-grade materials or spent nuclear fuel would cause the most significant contamination, but even medical supplies, such as radium, could be used. While this type of weapon has little traditional military use, it has the potential to serve well as a weapon of terror.