Spalling is something that happens to concrete, defined as the breaking, chipping, or fraying of concrete slabs that leave an uneven surface or edge, most often at joints or cracks.
Spalling is also a ballistics (terminal ballistics, in fact) phenomenon: some targets, when hit by a projectile, will produce fragments inside. Nasty, sharp, fast fragments. Notice that this can happen even when the projectile does not achieve penetration.
Solid stone is particularly prone to spalling. Some armored vehicles have a kevlar anti-spalling liner to reduce damage to the occupants. HESH rounds were designed precisely to produce spalling.

Spalling is also what happens when you knap flint or chert to make stone tools. When you hit the flint with the right pressure, conchoidal fracturing, or spalling, breaks off a thin flake of the stone.

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