- ground zero - the target of a projectile (as a bomb or missile)
--1 is a kind of target, target area
- ground zero - the site of the World Trade Center before it was destroyed
--2 is a kind of site, land site
- ground zero - the point of detonation (or above or below) of a nuclear weapon
--3 is a kind of point
- ground zero - the site of the World Trade Center before it was destroyed