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

Traveling is no longer a kryptonite for Rachel Brosnahan, thanks to the help of a witch. —EW.com, 17 July 2025

These tend to involve kryptonite, the substance that weakens the hero. —Matt Zoller Seitz, Vulture, 16 July 2025

The Dodgers have been the Braves' kryptonite this season, having won all five games against them. —Ben Verbrugge, MSNBC Newsweek, 4 May 2025

While there were a few memorable scenes, the script is its kryptonite. —Billie Melissa, MSNBC Newsweek, 8 July 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