bulletproof

• bullet-proof

bullet +‎ -proof

• IPA^(key): /bʊl.ɪtpɹuːf/

• Audio (AU)

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• Hyphenation: bul‧let‧proof

bulletproof (comparative more bulletproof, superlative most bulletproof)

1. (of a material) Capable of withstanding a direct shot by a bullet fired from a gun.

   A bulletproof window.

   A bulletproof vest.

2. (idiomatic) reliable, infallible, sturdy or error-tolerant.
3. (usually of an idea or concept) Unbreakable, very tough.

• (infallible): foolproof

bulletproof (third-person singular simple present bulletproofs, present participle bulletproofing, simple past and past participle bulletproofed)

1. To make proof against bullets.
2. (slang) to make resistant to failure.

   We have to bulletproof this program before we let the users at it; check every input, catch every possible flaw...it must not fail in use.