What is the relationship between being a viscous liquid and viscosity?

Answer 1

Viscosity is resistance to flow. A viscous liquid by definition will have more resistance to flow than a non-viscous liquid.

Answer 2

viscosity is the property of a liquid, in which it has a lot of friction between its molecules. this makes it sticky and difficult to flow.
all liquids have some amount of viscosity i.e., friction between its molecules. but those with high viscosity are called viscous liquids
example, honey, glass (glass is a liquid that has so much viscosity that it doesn't flow!)