1. n. 
A property of fluids and slurries that indicates their resistance to flow, defined as the ratio of shear stress to shear rate.
Poise is the unit for viscosity, equivalent to dyne-sec/cm2. Because one poise represents a high viscosity, 1/100 poise, or one centipoise (cP), is used for mud measurements. One centipoise equals one millipascal-second. Viscosity must have a stated or an understood shear rate to be meaningful. Measurement temperature also must be stated or understood.
See: bentonite, Bingham plastic model, breaker, Brookfield viscometer, capillary tube viscometer, carboxymethylcellulose, centipoise, derrickman, direct-indicating viscometer, funnel viscosity, gel strength, gyp mud, Herschel–Bulkley fluid, high-pressure, high-temperature viscometer, Marsh funnel, mud additive, Newtonian fluid, non-Newtonian fluid, pill, plastic fluid, power-law fluid, pseudoplastic, PVT, rheological property, rheology, shear rate, shear stress, VG meter, yield