[vis.cos.i.ty] n, pl -ties [ME viscosite, fr. MF viscosite, fr. ML viscositat-, viscositas, fr. LL viscosus viscous] (15c) 1: the quality or state of being viscous
2: the property of resistance to flow in a fluid or semifluid
3: the ratio of the tangential frictional force per unit area to the velocity gradient perpendicular to the direction of flow of a liquid--called also coefficient of viscosity