fallout

American  

[fawl-out] / ˈfɔlˌaʊt /

Or fall-out

noun

1. the settling to the ground of airborne particles ejected into the atmosphere from the earth by explosions, eruptions, forest fires, etc., especially such settling from nuclear explosions radioactive fallout.

2. the particles themselves.

3. an unexpected or incidental effect, outcome, or product.

   the psychological fallout of being obese.

4. effects; results.

   emotional fallout from a divorce.

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fallout British  

/ ˈfɔːlˌaʊt /

noun

1. the descent of solid material in the atmosphere onto the earth, esp of radioactive material following a nuclear explosion

2. any solid particles that so descend

3. informal side-effects; secondary consequences

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verb

1. informal to quarrel or disagree

2. (intr) to happen or occur

3. military to leave a parade or disciplinary formation

1. military the order to leave a parade or disciplinary formation

Etymology

Origin of fallout

First recorded in 1945–50; noun use of verb phrase fall out

Explanation

Fallout is the cloud of radioactive material that falls from the sky after a nuclear blast. Fear of the effects of fallout is just one reason some people are nervous about nuclear energy. Nuclear fallout settles on the ground and in the atmosphere after a nuclear bomb explodes or a reaction occurs at a damaged nuclear power plant. The dangers of this kind of fallout are enormous, including immediate death and long-term illness caused by breathing and eating the radioactive dust. Another kind of fallout is more figurative — it's any kind of negative effect or result, like the fallout from telling your family you're getting an enormous tattoo.

Example Sentences

Fallout: Mercor, whose clients have included OpenAI and Meta, has been hit with at least seven class-action lawsuits in recent weeks following a third-party data breach.

From The Wall Street Journal • Apr. 26, 2026

In recent years, Christopher Nolan’s Oppenheimer, the journalist Annie Jacobsen’s bestselling Nuclear War: A Scenario, and the video game–turned–TV show Fallout have tackled hypothetical armageddon.

From Slate • Mar. 13, 2026

Appeared in the February 4, 2026, print edition as 'The Epstein Files Fallout Hits the Innocent'.

From The Wall Street Journal • Feb. 3, 2026

While The Last of Us was wowing audiences, the producers of Fallout were putting the finishing touches to the first season of their adaptation, one which took a different approach to its source material.

From BBC • Dec. 17, 2025

Fallout from the meltdowns will affect the region for decades, possibly centuries.

From "Meltdown" by Deirdre Langeland