bulletproof
v.v. strong enough to stop bullets from going through it; also used to describe a plan or idea that cannot fail because it is so well-prepared.
v. impenetrable to small-arms projectiles; by extension, used to describe systems, arguments, or plans that are resilient to criticism or failure. Often used metaphorically in business or technical contexts to indicate extreme reliability.
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.
From bullet + proof, compounded in English during the nineteenth-century vogue for garments advertised as “pistol-proof” or “shot-proof” before the more business-like “bullet” supplanted the older synonym.
Typically used as an attributive adjective before the noun it modifies.