Which of the following describes a firearm that is not designed to be fired from the shoulder?

A firearm that is not designed to be fired from the shoulder is characterized by its design and intended usage. Handguns, which include revolvers and pistols, are specifically made to be fired with one hand, making them distinct from shoulder-fired weapons like rifles and shotguns. This design allows for greater maneuverability and ease of use in close-quarters situations.

Rifles and shotguns are typically designed for shoulder firing; they have longer barrels and stocks that facilitate aiming and stability when shouldered. Additionally, machine guns, while they can vary in design, are often also intended to be shouldered when fired. The key factor that identifies a handgun is its compactness and lack of a stock, setting it apart as a firearm meant to be operated in a different manner than those designed for shoulder use. Hence, identifying a handgun as a firearm not designed for shoulder use is accurate and reflects its intended operational context.