Definitions for "Ground Zero"
The almost instantly coined nickname for the World Trade Centre site itself.
The point on the surface of land or water at or vertically below or above the center of the burst of a nuclear weapon.
The point on the surface of land vertically below or above the center of a burst of a nuclear (or atomic) weapon; frequently abbreviated to GZ. For a burst over or under water the corresponding term is surface zero (SZ). Surface zero is also commonly used for ground surface and underground bursts.