Plunging fire is gunfire directed upon an enemy from an elevated position, or gunfire aimed so as to fall on an enemy from above.

In naval warfare plunging fire was often used to penetrate an enemy ship's thinner deck armor rather than firing directly at an enemy ship's side. Another method is in a form of indirect fire

Indirect fire

Indirect fire means aiming and firing a projectile in a high trajectory without relying on a direct line of sight between the gun and its target, as in the case of direct fire...

, by aiming the weapon, usually a machine gun or belt-fed grenade launcher, at such a degree that it is pointed over an elevated obstacle such as a hill that it may nearly graze it. The impact zone will be just that of the opposite side. The trajectory of the rounds will take effect and "plunge" greatly after travelling the determined range; in which the rounds will be falling from directly above vice from the front, increasing the chances of striking an advancing force in the cone of fire when no other technique becomes effective.

Both the howitzer

Howitzer

A howitzer is a type of artillery piece characterized by a relatively short barrel and the use of comparatively small propellant charges to propel projectiles at relatively high trajectories, with a steep angle of descent...

 and mortar

Mortar (weapon)

A mortar is an indirect fire weapon that fires explosive projectiles known as bombs at low velocities, short ranges, and high-arcing ballistic trajectories. It is typically muzzle-loading and has a barrel length less than 15 times its caliber....

provide this type of fire.