ultrathin
adjective
ul·tra·thin
ˌəl-trə-ˈthin 
: extremely or extraordinarily thin
ultrathin phones
ultrathin fashion models
The molecules ride on the surface like a film of soap and assemble themselves into an ultrathin layer about one-millionth of an inch thick.—
Mike May
Mike MayExamples of ultrathin in a Sentence
a new generation of flat-panel TVs that were ultrathin
Recent Examples on the Web
The ultrathin layer, developed by researchers led by Cho Jin-han, PhD, a professor at Korea University’s chemical and biological engineering department, prevents the formation of dangerous dendrites.
—Georgina Jedikovska, Interesting Engineering, 17 Oct. 2025
This iconic brow pencil is well-loved in the industry (and in the Allure office) for its ultrathin, retractable tube—no sharpener needed—and its ability to easily shape and fill in sparse sections with hair-like strokes.
—Sarah Kinonen, Allure, 1 Oct. 2025
Along with an ultrathin iPhone Air and other redesigns, the new phones come with a less flashy upgrade that could turn out to be the true killer feature.
—Lily Hay Newman, Wired News, 11 Sep. 2025
The Air, starting at $999, has an ultrathin design that is just 5.6 millimeters thick, about 28% thinner than the standard iPhone 16.
—Todd Spangler, Variety, 9 Sep. 2025
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Georgina Jedikovska, Interesting Engineering, 17 Oct. 2025
This iconic brow pencil is well-loved in the industry (and in the Allure office) for its ultrathin, retractable tube—no sharpener needed—and its ability to easily shape and fill in sparse sections with hair-like strokes.
—Sarah Kinonen, Allure, 1 Oct. 2025
Along with an ultrathin iPhone Air and other redesigns, the new phones come with a less flashy upgrade that could turn out to be the true killer feature.
—Lily Hay Newman, Wired News, 11 Sep. 2025
The Air, starting at $999, has an ultrathin design that is just 5.6 millimeters thick, about 28% thinner than the standard iPhone 16.
—Todd Spangler, Variety, 9 Sep. 2025
See All Example Sentences for ultrathin
Cite this Entry
“Ultrathin.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/ultrathin. Accessed 28 Oct. 2025.
Copy CitationMedical Definition
ultrathin
adjective
ul·tra·thin
ˌəl-trə-ˈthin
: exceedingly thin
ultrathin sections for use in electron microscopy
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