# kryptonite

/ˈkɹɪptəˌnaɪt/ (US) · CEFR B2 · Noun

Source: https://englishreference.com/word/kryptonite
Updated: 2026-05-19

## Definition

something that is very bad for you or makes you fail. It is a funny way to say that a person or thing is your worst enemy.

For teachers: a substance or factor that is extremely harmful or debilitating to a specific entity. In modern slang, it refers to a person or thing that causes significant failure or distress.

## Examples

- His lack of sleep is his own personal kryptonite.
- For many students, the final exam is their kryptonite because they struggle with the high-pressure environment.
- While the team was otherwise dominant, their inability to handle the pressure of the championship final proved to be their ultimate kryptonite.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.