the radioactive particles that settle to the ground after a nuclear explosion
"The emergency shelters were filled as the deadly fallout from the blast began settling on the surrounding fields."
any adverse and unwanted secondary effect
"a strategy to contain the fallout from the accounting scandal"
The event of small airborne particles falling to the ground in significant quantities as a result of major industrial activity, volcano eruption, sandstorm, nuclear explosion, etc.
"Residents were advised to stay indoors while heavy radioactive fallout from the test site settled on their roofs."