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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
Nia Bowers, USA Today, 15 June 2025
These vultures rely on powerful soaring techniques and can cover vast distances in search of carrion, making use of rising thermal currents to stay aloft with minimal energy expenditure.
—Scott Travers, Forbes.com, 14 June 2025
Josh Honeycutt, Outdoor Life, 26 Sep. 2024
Heever’s fresh, clear soprano soared up to the top high B like an eagle on thermals.
—Air Mail, 26 Apr. 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 18 Jun. 2025.
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