Definition of "ground zero" []

• The target of a projectile, such as a missile or bomb. (noun)
• The site directly below, directly above, or at the point of detonation of a nuclear weapon. (noun)
• 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). (noun)
• The starting point or most basic level: My client didn't like my preliminary designs, so I returned to ground zero. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "So the Grumleys had set up almost at ground zero of the NASCAR explosion: directly across from NASCAR Village, on the other side of parkway, just a bit down from the driveway that led to the parkway from the speedway headquarters, an admin building in art moderne aluminum."
• "In the past half-century, the meaning was extended to “the center of violent activity or sudden change,” and even to “the ultimate origin, very be-ginning,” as a near-synonym to the informal board-game phrase square one; as such, ground zero is lowercase."
• "Ed Mathias was a managing partner at the Carlyle Group—a powerful private-equity investment firm in D.C. that counts among its partners and clients ex-presidents, prime ministers, and Arabian princes, and is also ground zero for liberal conspiracy theorists."