- the land or water surface area directly below or above the point of detonation of a nuclear bomb
- the starting point
- the most basic condition or level
See ground zero in American Heritage Dictionary 4
- The target of a projectile, such as a missile or bomb.
- The site directly below, directly above, or at the point of detonation of a nuclear weapon.
- The center of rapid or intense development or change: “The neighborhood scarcely existed five years ago, but today it is the ground zero from which designer shops and restaurants radiate” (Robert Clark).
- The starting point or most basic level: My client didn't like my preliminary designs, so I returned to ground zero.