n, pl  -ties  1  :  the quality of being viscous : esp  :  the property of resistance to flow in a fluid or semifluid  2  :  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  .
 
 
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2024.