Definition of kryptonite
- a substance that causes the comic-book character Superman to become weak when he is exposed to it
- often used to describe something likened to kryptonite in causing someone's weakness, failure, etc
Usage examples of kryptonite
In the comic, kryptonite made Superman weak when it was brought near him.
Public speaking is his kryptonite; even a short presentation makes him freeze.
Poor battery life became the new phone's kryptonite during long trips.