Fallout is the radiation that affects a particular place or area after a nuclear explosion has taken place.
They were exposed to radioactive fallout during nuclear weapons tests.
他们在核武器试验过程中暴露于放射性核辐射中。
If you refer to the fallout from something that has happened, you mean the unpleasant consequences that follow it.
Grundy lost his job in the fallout from the incident.
格伦迪因该事故丢了工作。