What term describes an explosion of a bomb or projectile that occurs above the surface of the ground?

The term that best describes an explosion of a bomb or projectile that occurs above the surface of the ground is "Air Burst." This phenomenon typically refers to an explosion that occurs at a certain height in the air rather than upon impact with the ground. Air bursts are often designed to maximize the blast radius and the effectiveness of the explosion by dispersing energy across a wider area, thus increasing the damage caused to targets below.

In contrast, surface detonations occur when the explosive device detonates upon impact with the ground, leading to different effects and damage patterns. Ground Impact explosions happen at the exact point where the device strikes the earth, resulting in cratering and localized destruction. The term "Sky Explosion" is not commonly used in explosive ordnance terminology and does not have a defined meaning in the context of explosive detonations. Therefore, "Air Burst" is the most appropriate choice among the available options.