Ablative armor is armor designed to negate damage by itself being damaged or destroyed through the process of ablation. In contemporary spacecraft, ablative plating is most frequently seen as an ablative heat shield for a vehicle that must enter atmosphere from orbit, such as on nuclear warheads, or space vehicles like the Mars Pathfinder probe. The idea is also commonly encountered in science fiction.

Ablative armor is selective armor. Usually all the armored vehicles are uniformly protected but some are partially and selectively re enforced. This gained popularity when the USA invaded Iraq to topple Saddam Hussein. To prevent against suicide attacks most of the Hummers were partially re-enforced on a single side where the commanding officer sat. This drew a lot of criticism but continues to remain popular.
These plates are usually made of a carbon fiber and can withstand impressive volumes of pressure and heat.