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kryptonite

American

[krip-tuh-nahyt] / ˈkrɪp təˌnaɪt /

noun

Usually Kryptonite a fictional radioactive substance that is the only thing capable of hurting or weakening the otherwise invulnerable superhero Superman.

Exposure to Kryptonite nullifies Superman's powers and immobilizes him with pain.
Sometimes Kryptonite something that a person or thing cannot defend against or defeat; a nemesis or bête noire.

The team has not found a way to stop the triple option attack, which has been their kryptonite over the last several years.
Garlic oil is kryptonite for aphids.

Etymology

Origin of kryptonite

Coined in 1943 by writer and producer George Lowther (1913–1975); krypton ( def. ) + -ite ¹ ( def. )

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

kryptonite

"Their biggest kryptonite is real estate cost," York warned, pointing to a brutal Manhattan retail landscape where average asking rents are between $350 and $700 per square foot.

From BBC ● Jul. 12, 2026

Early in 2026, in fact, tech was the market’s kryptonite, with once-hot software companies largely to blame for the trouble.

From Barron's ● May 1, 2026

“So 6,475 strike behaves like kryptonite for the market; it can repel price from above and below,” Kizemchuck said.

From MarketWatch ● Mar. 28, 2026

Plus, her ire and rage is kryptonite against those who’ve been “joined.”

From Los Angeles Times ● Dec. 24, 2025

“You do know that the word fine is basically kryptonite to a therapist’s ears, right?”

From "Far from the Tree" by Robin Benway

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Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023