Hc verma, concepts of Physics, vol 1 pg 258
We define pressure of fluid at the point A as : $P= F/\Delta S$. For a homogeneous and non-viscous fluid, this quantity does not depend on orientation of $\Delta S$ and hence we talk of pressure at a point.
Why did the author stress that the definition holds only for non-viscous fluids? What happens to viscous fluids? Does the pressure depend on orientation?