That to me is the most correct definition. A bullet is designed with a particular performance criteria in mind. Did the bullet live up to its design criteria? Misapplication or misaligned expectations is a different discussion altogether. To be utterly clear, I do not know if one could or should shoot a pig in the forehead with a soft bullet. If yes, then bullet failure.

BTW: killing deer and elk with an automobile bumper is the most expensive bullet of all!!!!!!