Fallout is radioactive dust after an explosion, or the bad consequences of an act. Nuclear fallout, a fallout shelter, the political fallout.
The literal kind is debris sucked up, made radioactive and dropped downwind, which is why the danger reaches far beyond the blast. The figurative sense is now much commoner: the fallout from a decision is the trouble that follows it.
1nounfalloutRadioactive dust after an explosion.
“After the Chernobyl disaster, fallout from the reactor spread across much of Europe.”
2nounbadThe bad consequences of an act.
“The minister resigned, but the political fallout from the scandal lasted for months.”
fallout is a consequence.
From the phrasal verb fall out, coined in the 1950s for what descends after a nuclear test.
a deverbal from fall out; fall + out.
Etymology from Wiktionary, CC BY-SA