Able to withstand or resist armor-piercing weapons; impenetrable or impossible to damage with conventional weapons.
Compound from armor and proof (meaning resistant to). This term evolved alongside military technology as stronger materials were developed that could resist known weapons.
The phrase 'armorproof' is almost a joke in military engineering because once someone invents something 'armorproof,' someone else invents armor-piercing ammunition—it's an endless arms race.
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