What characteristic defines a 'weapon of mass destruction' based on U.S. law?

A 'weapon of mass destruction' is defined primarily by its intended purpose to cause widespread harm, particularly severe casualties among large populations. This definition aligns with various U.S. laws and regulations that aim to categorize weapons based on their potential to inflict significant damage or loss of life. The focus here is on the devastating impact that such weapons have, which can encompass nuclear, biological, and chemical agents.

While factors like production cost, the need for federal licensing, and operational secrecy may play roles in how these weapons are regulated or controlled, they do not fundamentally define a weapon of mass destruction. The key characteristic is the ability to inflict large-scale harm, making it a major concern for national and international security. In this context, the emphasis on capacity for severe casualties is crucial in understanding the nature of such weapons and their implications for public safety.