# bulletproof

/ˈbʊɫətˌpɹuf/ (US) · /bˈʊlɪtpɹˌuːf/ (UK)

Source: https://englishreference.com/word/bulletproof
Updated: 2026-08-27

## Senses

### 1. stopping bullets

adjective · CEFR B2

made of a strong material that stops bullets from passing through it.

For teachers: capable of withstanding a direct shot from a firearm without being penetrated.

- The security guards wore bulletproof vests for protection during the transport.
- The diplomatic vehicle was fitted with bulletproof glass and reinforced plating to ensure the safety of the officials during transit through the conflict zone.

### 2. impossible to fail

adjective · CEFR B2 · Informal

so well-planned or strong that it cannot be broken, criticized, or defeated.

For teachers: infallible or robust; resistant to failure, error, or external criticism.

- She presented a bulletproof argument that convinced the entire board.
- The legal team spent months building a bulletproof case, ensuring that every piece of evidence was verified and every loophole closed.

### 3. to make resistant to failure

verb · CEFR C1 · Informal · Technical

to improve a plan or a piece of software so that it will not fail.

For teachers: to reinforce a system, plan, or process against potential failure or error.

- We need to bulletproof the new app before we release it to the public.
- The engineers worked through the weekend to bulletproof the server architecture against the expected surge in traffic during the product launch.

Usage: Often used in business or software development contexts.

## Examples

- The guards wear bulletproof vests for protection.
- The lawyer spent weeks checking every detail to ensure her client's defense was bulletproof before the trial began.
- In a volatile market, investors seek bulletproof strategies that can withstand sudden shifts in sentiment without compromising the underlying capital.

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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.