ther·​mo·​nu·​cle·​ar ˌthər-mō-ˈnü-klē-ər How to pronounce thermonuclear (audio)
-ˈn(y)ü-kyə-lər How to pronounce thermonuclear (audio)
: of, relating to, or employing transformations in the nuclei of atoms of low atomic weight (such as hydrogen) that require a very high temperature for their inception (as in the hydrogen bomb or in the sun)
thermonuclear reaction
thermonuclear weapon
: of, utilizing, or relating to a thermonuclear bomb
thermonuclear war
a thermonuclear attack

Example Sentences

Hydrogen bombs are thermonuclear weapons.
Recent Examples on the Web Unlike our own sun, which will shine for billions of years, more massive stars can burn through their thermonuclear fuel in only a few million years before sloughing off their outer layers and exploding in a dramatic supernova. Allison Parshall, Scientific American, 17 Mar. 2023 Modern thermonuclear devices are complex bits of machinery designed to initiate a specific explosive sequence, sometimes called a fission-fusion-fission reaction, which releases a massive amount of energy. WIRED, 27 Feb. 2023 Detonate a thermonuclear weapon to blast a crack several hundred meters deep in Earth’s surface. Tim Folger, Discover Magazine, 13 July 2014 But a full draft opinion has never leaked to the press in the modern history of the court, and the reaction inside the marble palace will likely be thermonuclear. Matt Ford, The New Republic, 3 May 2022 DeChambeau’s controversies emerge from his almost thermonuclear proclivity for violating golf’s behavioral norms. John Guaspari, National Review, 26 Sep. 2021 Even the invention of the atom bomb didn’t end the primacy of carriers; instead, carriers became a platform for delivering thermonuclear weapons. Kyle Mizokami, Popular Mechanics, 24 Sep. 2021 During the Cold War, the U.S., even with NATO, didn’t have primacy over the Soviet Union and Warsaw Pact for one reason: The Soviets saw a war as a fight to the finish in which nuclear and thermonuclear weapons would be used. WSJ, 29 May 2020 Many are the remains of massive stars that collapsed after burning through their thermonuclear trust funds. Dennis Overbye, New York Times, 6 May 2020 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'thermonuclear.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History


International Scientific Vocabulary

First Known Use

1938, in the meaning defined at sense 1

Time Traveler
The first known use of thermonuclear was in 1938

Dictionary Entries Near thermonuclear

Cite this Entry

“Thermonuclear.” Dictionary, Merriam-Webster, Accessed 30 Mar. 2023.

Kids Definition


ther·​mo·​nu·​cle·​ar ˌthər-mō-ˈn(y)ü-klē-ər How to pronounce thermonuclear (audio)
: of or relating to the transformations in the nucleus of atoms of low atomic weight (as hydrogen) that require a very high temperature (as in the hydrogen bomb or in the sun)
a thermonuclear reaction
a thermonuclear weapon

More from Merriam-Webster on thermonuclear

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Which Came First?

  • baby chick with a brown egg
  • hot take or cold shoulder?
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!

Solve today's spelling word game by finding as many words as you can with using just 7 letters. Longer words score more points.

Can you make 12 words with 7 letters?