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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
Sydney Sasser, Arkansas Online, 30 Oct. 2025
The tests were conducted under various loads and combustion conditions, allowing for an assessment of the impact of flame position on the boiler’s thermal performance and heating surface operation.
—Prabhat Ranjan Mishra, Interesting Engineering, 30 Oct. 2025
Sian Babish, PEOPLE, 23 Oct. 2025
Android phones have been using vapor chambers to help manage thermals for years, but the 17 Pro and Pro Max are the first two iPhones to have one.
—PC Magazine, 18 Sep. 2025
See All Example Sentences for thermal
Cite this Entry
“Thermal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/thermal. Accessed 4 Nov. 2025.
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