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From the book What If? of XKCD when talking about super strong winds:
The flying debris would pulverize anything that wasn't nuclear-hardened.
What does nuclear-hardened mean? The closest result from Google for this term is Radiation hardening. But radiation hardening simply means making a device withstand-able in high radiation environment. The context doesn't mention anything about radiation, or radiation wind (if it even exists), just air wind.
So what does nuclear-hardened mean?
Nuclear hardened means able to withstand the nearby detonation of a nuclear device. I used to work* in such a building, part of the USAF SAGE program of the 1950s & 60s: https://en.wikipedia.org/wiki/Semi-Automatic_Ground_Environment The walls & floors were about 2-3 ft of reinforced concrete, intended to withstand a nuclear detonation on the airfield about 1/4 mile away.
*Not when it was in active military use, but some decades later, when it had been converted to an academic research facility.
