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

Synonyms

• fine
• hairline
• narrow
• needlelike
• paper-thin
• skinny
• slender
• slim
• slim-jim
• thin

Examples of ultrathin in a Sentence

a new generation of flat-panel TVs that were ultrathin

Recent Examples on the Web

The ultrathin blade made of Japanese carbon steel won't get discolored as easily as others, but the lack of information regarding the hardness of its blade gives me pause as to its performance in the long term. —Molly Higgins, Wired News, 2 May 2025

The cultural ideal for women is again ultrathin — but under a new banner of self-love. —Natasha Frost, New York Times, 1 May 2025

And there is a range of materials that can serve as flexible substrates for TFTs, such as ultrathin glass, stainless steel foils, and plastic films. —IEEE Spectrum, 26 Aug. 2013

Most cracking or damage done to windows by a vacuuming robotic window cleaner is to ultrathin windows or to windows that have already been damaged in some way. —Bestreviews, Chicago Tribune, 11 Apr. 2025

Word History

First Known Use

1851, in the meaning defined above

Medical Definition

ultrathin

adjective

ul·​tra·​thin ˌəl-trə-ˈthin 

: exceedingly thin

ultrathin sections for use in electron microscopy