Fragmentation
A bullet breaking into multiple pieces on impact, which spreads damage across a wider area while cutting overall penetration depth.
Fragmentation is the terminal behavior in which a bullet breaks apart on impact rather than holding together, scattering pieces that spread tissue damage over a broader area. It sits at the far end of the deformation spectrum from controlled expansion, and it is a central topic in terminal ballistics because the tradeoff it carries is significant.
When a bullet fragments, the loss of mass and frontal coherence sharply reduces how deep the projectile drives, so penetration falls even as surface damage rises. Some designs court this on purpose: a frangible bullet is built to come apart readily to limit over-penetration or ricochet, while in a hunting bullet uncontrolled fragmentation is usually a fault to be engineered out.