IS The movement of substances from an area of higher hydrostatic pressure to an area of lower hydrostatic pressure is called diffusion?

No, the movement of substances from an area of higher hydrostatic pressure to an area of lower hydrostatic pressure is not called diffusion. Diffusion is the movement of substances from an area of higher concentration to an area of lower concentration. The movement of substances from an area of higher hydrostatic pressure to an area of lower hydrostatic pressure is called filtration. Filtration is a passive process driven by the pressure difference across a membrane.