n. (pl. -ies) 1 the quality or degree of being viscous. 2 Physics a (of a fluid) internal friction, the resistance to flow. b a quantity expressing this. dynamic viscosity a quantity measuring the force needed to overcome internal friction. kinematic viscosity a quantity measuring the dynamic viscosity per unit density. viscosimeter n.
[ ME f. OF viscosité or med.L viscositas (as VISCOUS) ]