Which term describes an underpowered round that fails to function correctly?

The term that describes an underpowered round that fails to function correctly is "squib." A squib load occurs when there is insufficient powder in the cartridge, resulting in a projectile that may not exit the barrel with enough force. This can be particularly dangerous; if the bullet does not clear the barrel, a subsequent round fired can cause a dangerous blockage and potentially lead to a catastrophic failure of the firearm.

Understanding this term is crucial for firearm safety and operation, as recognizing a squib load is important for preventing more severe complications. Squib loads often manifest as a noticeably quieter report and can lead to immediate inspection of the firearm to ensure it is safe to handle before attempting to fire again.