Frangible
A bullet engineered to crumble into fine particles when it strikes a hard surface, instead of penetrating or ricocheting back.
Frangible bullets are pressed from powdered metal, usually copper or a copper-tin blend, with no traditional lead core. On contact with steel or another hard backstop they disintegrate into dust rather than splashing back, which is why they show up on close-range steel courses and in tight indoor ranges.
For long-range work they fill a specialized role rather than a general one. The compressed-powder construction gives up the consistent jacket and core of a match-grade bullet, so ballistic coefficient and downrange uniformity both drop off. Their real strength is safety on hard targets up close, where that close-range job is exactly what they do well.