Which of the following refers to a bomb or grenade that fails to fire properly?

The term that refers to a bomb or grenade that fails to fire properly is a misfire. A misfire can occur due to various reasons, such as a failure in the ignition system, a defect in the propellant, or any obstruction that prevents the explosive from functioning as intended. Understanding the implications of a misfire is crucial in explosive ordnance disposal, as it requires the technician to approach the situation with caution due to the potential hazards involved.

In contrast, the other options carry different meanings. A malfunction may refer broadly to any failure in functionality but does not specifically indicate that a device has failed to fire. High explosive refers to a type of explosive material characterized by a rapid reaction and high detonation velocity; it does not denote a reliability issue. An improvised explosive device (IED) is a homemade bomb that is often designed to be detonated by unconventional means, rather than a device that has failed to fire. Therefore, misfire is the most accurate term to describe a bomb or grenade that does not operate as intended.