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

Perhaps Alex Pereira is still Procházka’s kryptonite, but no other light heavyweight in the world has beaten him in 12 years. —Brian Mazique, Forbes, 20 Jan. 2025

However, as productive as Miami was offensively, turnovers were once again the Hurricanes’ kryptonite. —Gio Alonso, Miami Herald, 5 Jan. 2025

Witnessing how Drake's superpower has become his kryptonite is frustrating. —Kia Turner, refinery29.com, 28 Nov. 2024

Tomlin has been Jackson’s kryptonite throughout the Ravens QB’s career. —Mike Defabo, The Athletic, 31 Dec. 2024

Word History

Etymology

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

First Known Use

1943, in the meaning defined above