kryptonite
noun
kryp·to·nite
ˈkrip-tə-ˌnīt 
variants
or Kryptonite
in stories
: a substance that causes the comic-book character Superman to become weak when he is exposed to it
Note: In Superman stories, kryptonite in its most familiar form is a green mineral that originated as part of Superman's home planet of Krypton and that falls to Earth as a meteorite.
Superman tended to get more bummed out by Kryptonite than by anything going on in Clark Kent's life …—
Tom Russo
—often used to describe something likened to kryptonite in causing someone's weakness, failure, etc.Tom RussoIn his career Thome has hit less than .240 against lefties. Lefthanded power pitching is Thome's Kryptonite …—Joe Posnanski
Joe PosnanskiIronic people always dissolve when confronted with earnestness, it's their kryptonite.—Gillian Flynn
Gillian Flynn"Thin people know they need to either limit exposure to certain foods that trigger appetite or limit the quantity or frequency of those foods," says Gullo, whose personal kryptonite is pizza.—Lorie Parch
Lorie ParchEffortlessly good-looking, he was also a talented writer—that combo was my kryptonite.—Taylor Orci
Taylor OrciExamples of kryptonite in a Sentence
Recent Examples on the Web
Palace have emerged as their kryptonite since, winning each of their last three encounters 10-1 on aggregate.
—Anantaajith Raghuraman, New York Times, 11 Sep. 2025
Since arriving in the big leagues, Minnesota Twins starter Joe Ryan has been the Kansas City Royals’ personal kryptonite.
—Kansas City Star, 7 Sep. 2025
With his extreme sensitivity to all sound, Niki’s kryptonite is a blue airhorn that Uri uses to control him once Niki begins to actively look for a way out.
—Caleb Hammond, IndieWire, 1 Sep. 2025
John Kosko of Pro Football Focus has identified Jackson's playoff problems as his biggest kryptonite entering the 2025 campaign.
—Matthew Schmidt, MSNBC Newsweek, 28 Aug. 2025
See All Example Sentences for kryptonite
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Anantaajith Raghuraman, New York Times, 11 Sep. 2025
Since arriving in the big leagues, Minnesota Twins starter Joe Ryan has been the Kansas City Royals’ personal kryptonite.
—Kansas City Star, 7 Sep. 2025
With his extreme sensitivity to all sound, Niki’s kryptonite is a blue airhorn that Uri uses to control him once Niki begins to actively look for a way out.
—Caleb Hammond, IndieWire, 1 Sep. 2025
John Kosko of Pro Football Focus has identified Jackson's playoff problems as his biggest kryptonite entering the 2025 campaign.
—Matthew Schmidt, MSNBC Newsweek, 28 Aug. 2025
See All Example Sentences for kryptonite
Cite this Entry
“Kryptonite.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/kryptonite. Accessed 14 Sep. 2025.
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