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Synonyms

meltdown

American  
[melt-doun] / ˈmɛltˌdaʊn /

noun

  1. the melting of a significant portion of a nuclear-reactor core due to inadequate cooling of the fuel elements, a condition that could lead to the escape of radiation.

  2. a quickly developing breakdown or collapse.

    a bond-market meltdown;

    the meltdown of a marriage.

  3. Informal. a sudden loss of control over one’s feelings or behavior.

    My toddler had a meltdown when I tried to leave the house.
meltdown British  
/ ˈmɛltˌdaʊn /

noun

  1. (in a nuclear reactor) the melting of the fuel rods as a result of a defect in the cooling system, with the possible escape of radiation into the environment

  2. informal a sudden disastrous failure with potential for widespread harm, as a stock-exchange crash

  3. informal the process or state of irreversible breakdown or decline

    the community is slowly going into meltdown
"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
meltdown Scientific  
/ mĕlt′doun′ /

  1. Severe overheating of a nuclear reactor core, resulting in melting of the core and escape of radiation.

meltdown Cultural  

  1. The most serious accident that can occur at a nuclear reactor. In a meltdown, the radioactive material in the reactor becomes very hot, melting some or all of the fuel in the reactor. A meltdown may or may not be followed by the release of radioactive material to the environment. A partial meltdown, with very little external radiation, occurred at Three Mile Island (see also Three Mile Island) in 1979; a complete meltdown happened at Chernobyl in 1986.

Etymology

Origin of meltdown

First recorded in 1960–65; noun use of verb phrase melt down

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

The backdrop for the meltdown was that the issuers of those mortgage securities paid no attention to the credit quality of the underlying assets after they sold them to banks and other financial institutions.

From MarketWatch • Apr. 14, 2026

Carlyle Group’s flagship private-credit interval fund is the latest to be hit with a wave of share-redemption requests, as investor fears about a potential private-credit meltdown continue.

From The Wall Street Journal • Apr. 9, 2026

Medvedev has become infamous for his outbursts - most notably at last year's US Open, where he had a meltdown after a photographer walked on court mid-match.

From BBC • Apr. 8, 2026

A tradwife influencer’s public meltdown or toxic relationship prods at the artifice and hypocrisy of aspirational Christian content, but these scandals also reveal an uncomfortable relationship between creators and their audience.

From Los Angeles Times • Apr. 7, 2026

That was about three tons of monkey meat—a biological nuclear reactor having a core meltdown.

From "The Hot Zone" by Richard Preston

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.