verb

1. To make proof against bullets.

2. 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.”

adjective

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

   “A bulletproof window.”

2. Reliable, infallible, sturdy or error-tolerant.

3. (usually of an idea or concept) Unbreakable, very tough.

Synonyms: foolproof