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
Real suffering is kryptonite to rich-people-problems entertainment (which is probably also why The Real Housewives of New York City imploded, this past January, in a season finale where one cast member accused another of insensitivity towards the former’s traumatic experience as a rape survivor).
—Judy Berman, Time, 13 Aug. 2025
One of them, as anyone can tell you, is kryptonite, the green mineral that can substantially weaken and even harm the bulletproof man.
—EW.com, 10 June 2025
But the Aztecs, with their length and athleticism and ability to switch ball screens with a big who can move his feet, are his kryptonite.
—Mark Zeigler, San Diego Union-Tribune, 17 Feb. 2025
The finding now gives scientists the chance to discover the kryptonite that will sap them of this extra boost of strength.
—New Atlas, 3 Aug. 2025
See All Example Sentences for kryptonite
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Judy Berman, Time, 13 Aug. 2025
One of them, as anyone can tell you, is kryptonite, the green mineral that can substantially weaken and even harm the bulletproof man.
—EW.com, 10 June 2025
But the Aztecs, with their length and athleticism and ability to switch ball screens with a big who can move his feet, are his kryptonite.
—Mark Zeigler, San Diego Union-Tribune, 17 Feb. 2025
The finding now gives scientists the chance to discover the kryptonite that will sap them of this extra boost of strength.
—New Atlas, 3 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 24 Aug. 2025.
Copy CitationLove words? Need even more definitions?
Merriam-Webster unabridged
Share