Definition - What does Viscosity Cup mean?
A viscosity cup is an instrument used to determine a fluid's thickness and flow resistance. This is done by introducing a sample of the fluid into a container with a hole in its bottom and recording the time it takes for the container to empty when draining the fluid through the opening. The faster the fluid is drained, the less viscous the fluid is and vice versa.
Corrosionpedia explains Viscosity Cup
Determining fluid viscosity is helpful in corrosion prevention. A highly viscous substance is less likely to cause corrosion because it has a lower rate of freely moving molecules to react with a metallic surface.