# foolproof

/ˈfuɫˌpɹuf/ (US) · /fˈuːlpɹuːf/ (UK) · CEFR B2 · Verb

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

## Definition

describing a plan or method that is very difficult to fail. You use this when you want to say something is safe and reliable.

For teachers: describing a plan, method, or system that is highly unlikely to fail or be defeated. Often used to describe security measures or simple instructions that are hard to mess up.

## Examples

- The new security system is foolproof.
- The recipe is foolproof, so even if you are a beginner, you will get great results.
- The architect designed the building with a foolproof drainage system to prevent any water damage during the heavy seasonal rains.

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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.