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.

In his career Thome has hit less than .240 against lefties. Lefthanded power pitching is Thome's Kryptonite …

—Joe Posnanski

Ironic people always dissolve when confronted with earnestness, it's their kryptonite.

—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

Effortlessly good-looking, he was also a talented writer—that combo was my kryptonite.

—Taylor Orci

Examples of kryptonite in a Sentence

Recent Examples on the Web

In 1986, a tree on Central Park West became Superman's kryptonite. —Kate Hogan, PEOPLE, 27 Nov. 2025

Like all creatures of the Upside Down, heat is its kryptonite, and Kay toys with Hopper by toying with the temperature in the room. —Maggie Fremont, Vulture, 27 Nov. 2025

But to the Joined, Carol could easily be the villain since her anger is their kryptonite. —Brian Davids, HollywoodReporter, 10 Nov. 2025

Fritz has, in fact, turned into even more kryptonite for Zverev, beating him in their past six meetings. —Charlie Eccleshare, New York Times, 10 Nov. 2025

Word History

Etymology

Krypton, Superman's home planet + -ite entry 1

First Known Use

1943, in the meaning defined above

Rhymes for kryptonite

• acolyte
• aconite
• allanite
• alunite
• amberlite
• ammonite
• amorite
• amphitrite
• analyte
• anchorite
• andesite
• anhydrite