What does the phrase ground zero mean?

English Language Learners Definition of ground zero

: the point on the earth’s surface directly above, below, or at which an explosion (especially a nuclear explosion) occurs. : the central point in an area of fast change or intense activity. : the beginning state or starting point.

What is the term ground zero used for?

ground zero in American English

US. the land or water surface area directly below or above the point of detonation of a nuclear bomb. Slang.

What’s another word for ground zero?

What is another word for ground zero?
hub heart
middle pivot
nub kernel
headquarters place
foundation polestar