Bulletproof (adjective)

1. Capable of stopping bullets from penetrating.
2. Unable to be damaged or defeated by something.

Origin:

Late 19th century: from bullet + proof.

Examples:

1. The police officers were wearing bulletproof vests.
2. The company's financial position is bulletproof.
3. The car is bulletproof, no one can break the windows or penetrate it.
4. The fortress was built with bulletproof walls.
5. The evidence was so strong that it was almost bulletproof.