Isostatic refers to a type of vertical movement or deformation in the Earth's crust that occurs when the pressure from an underlying layer causes it to rise relative to the surrounding area. This can happen due to various geological processes, such as the melting of ice sheets after glaciation, which can cause areas of land to rise and become isostatic. The term comes from the Greek words "iso" meaning equal or same, and "static," referring to a stationary state or balance.