ther·​mal | \ ˈthər-məl How to pronounce thermal (audio) \

Definition of thermal

 (Entry 1 of 2)

1a : of, relating to, or caused by heat thermal stress thermal insulation
b : being or involving a state of matter dependent upon temperature thermal conductivity thermal agitation of molecular structure
c : having low energies of the order of those due to thermal agitation thermal neutrons
2 : designed (as with insulating air spaces) to prevent the dissipation of body heat thermal underwear
3 [ Latin thermae public baths, from Greek thermai, plural of thermē ] : of, relating to, or marked by the presence of hot springs thermal waters



Definition of thermal (Entry 2 of 2)

: a rising body of warm air

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Other Words from thermal


thermally \ ˈthər-​mə-​lē How to pronounce thermally (audio) \ adverb

Did You Know?

In days gone by, much of the male population of the northern states in the cold months would wear a garment of thermal underwear covering the entire body, called a union suit. Union suits kept sodbusters, cowboys, and townsfolk alike not only warm but also itchy and a little on the smelly side (back when bathing once a week was considered the height of cleanliness). Thermal imaging is photography that captures "heat pictures"--rather than ordinary light pictures--of objects. And thermal pollution occurs when industrial water use ends up warming a river in a damaging way. Small-plane pilots use thermal as a noun for a warm updraft, often over a plowed field or desert, that lifts their wings, just as it enables hawks to soar upward without moving their wings.

Examples of thermal in a Sentence

Recent Examples on the Web: Adjective

Some of the drones have thermal-imaging and can map an area in 3D or zoom into an object using their camera lenses. Shannon Liao, The Verge, "New York City cops will fly a drone over the New Year’s Eve celebration at Times Square," 30 Dec. 2018 Technology—including drones with thermal imaging to detect leaks along with improvements in horizontal drilling—boosted productivity. The Editorial Board, WSJ, "How America Broke OPEC," 14 Dec. 2018 My first exposure to thermal-imaging cameras was around 2006. Andrew Northshield, Popular Mechanics, "Firefighter Reviews New Thermal-Imaging Camera," 21 Nov. 2018 Start with a thermal base layer, like Uniqlo’s Heattech leggings or Vince’s ribbed half-zip top, that can be worn either hidden or exposed. Madeline Fass, Vogue, "Survive the Rest of Winter With These 4 Essential Layering Tips," 7 Feb. 2019 This allows solar thermal systems to keep sending energy to the grid well after the sun goes down. Megan Geuss, Ars Technica, "Using molten salt to store electricity isn’t just for solar thermal plants," 24 Dec. 2018 Visitors have been boiled alive in the park's thermal springs, according to the paper. Amy Lieu, Fox News, "Viral video shows man trying to bathe feet in Yellowstone's thermal hot springs: report," 25 Sep. 2018 The premise is that Track Mode readies the car for performance driving heroics, remapping the stability control and thermal management systems for the rigors of racetrack duty. Ezra Dyer, Popular Mechanics, "Electric Slide: We Drove the Tesla Model 3 in the Snow to See How It Fares as a Rally Car," 21 Feb. 2019 Garmin says the Instinct is built to military standards for thermal, shock, and water resistance (the latter rated to 100 meters). Dani Deahl, The Verge, "The Garmin Instinct is a rugged smartwatch for outdoor activities," 11 Oct. 2018

Recent Examples on the Web: Noun

That alone is big news, but there are other welcome improvements with this generation, from display and color choices to thermals. Melissa Riofrio, PCWorld, "Finally! The new Dell XPS 13 puts the camera in the right place," 8 Jan. 2019 Take thermals, columns of rising air that form when the ground below warms through sunlight. David Grossman, Popular Mechanics, "Vultures Use Social Networks to Share Crucial Flight Information," 8 Nov. 2018 Matek is a new base-layer brand built for the slopes, but its thermals are chic enough to wear on their own with a skirt or jeans. Anny Choi, Vogue, "5 Cold-Weather Styling Tricks You Can Take to the Office," 19 Jan. 2019 The turbo boosting should also be smarter, able to push the processor closer to its thermal and power limits. Peter Bright, Ars Technica, "Second-generation Threadripper goes on sale: $1,799 for 32 cores," 6 Aug. 2018 Feel the heat Solar thermal revolves around transfers of heat. John Timmer, Ars Technica, "New material could up efficiency of concentrated solar power," 19 Oct. 2018 The raptor will tell you where the thermals — the uplifting air currents — are. Alan Berner, The Seattle Times, "Go, hawks: Sailplane pilots look to birds for flying tips," 23 Nov. 2018 Officials are trying to start up several other thermal and hydroelectric plants to get at least some power back on the island. Fox News, "The Latest: 9 dead, 30 missing in northern Japan quake," 6 Sep. 2018 Apple has generally chosen not to go with the highest-end laptop GPUs in the MacBook Pro line, because those GPUs have necessarily come with big compromises in thermals and portability. Samuel Axon, Ars Technica, "2018 15-inch MacBook Pro review: Better, faster, stronger?," 24 July 2018

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

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First Known Use of thermal


1742, in the meaning defined at sense 3


1933, in the meaning defined above

History and Etymology for thermal


Greek thermē

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Statistics for thermal

Last Updated

16 Apr 2019

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Time Traveler for thermal

The first known use of thermal was in 1742

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English Language Learners Definition of thermal

 (Entry 1 of 2)

: of, relating to, or caused by heat
: designed to keep you warm by preventing heat from leaving your body
: having hot water flowing out of the ground



English Language Learners Definition of thermal (Entry 2 of 2)

: a rising current of warm air that is produced when the sun heats an area of the ground
British : thermal clothing or underwear


ther·​mal | \ ˈthər-məl How to pronounce thermal (audio) \

Kids Definition of thermal

: of, relating to, or caused by heat thermal insulation


ther·​mal | \ ˈthər-məl How to pronounce thermal (audio) \

Medical Definition of thermal

1 : of, relating to, or caused by heat tactile and thermal senses
2 : being or involving a state of matter dependent upon temperature thermal agitation of molecular structure

Other Words from thermal

thermally \ -​mə-​lē How to pronounce thermally (audio) \ adverb

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More from Merriam-Webster on thermal

Rhyming Dictionary: Words that rhyme with thermal

Spanish Central: Translation of thermal

Nglish: Translation of thermal for Spanish Speakers

Britannica English: Translation of thermal for Arabic Speakers

Comments on thermal

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a sum of money that is sent as a payment

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