Definition - What does Viscosity mean?
Viscosity is the state of being thick, sticky, and semi-fluid in consistency due to internal friction. It can be described as the resistance of any liquid to flow. Liquids with higher viscosity are more resistant to flow than liquids with a lower viscosity. Liquids with lower viscosity are less resistant to flow and flow more easily than liquids with higher viscosity.
Trenchlesspedia explains Viscosity
To determine the viscosity of drilling fluid and slurry, the fluid or slurry may be poured through a Marsh funnel. The measurement of viscosity for these products is expressed in "seconds per quart" (sec/qt), or how many seconds it takes a quart of the slurry or fluid to exit the funnel.
One quart of water, with no additive chemicals or solids, takes 26 seconds to leave the Marsh funnel, which means its viscosity is 26 seconds per quart.