Have a look here http:/dictionary.reference.com/browse/viscous
Viscosity it how thick or thin a fluid is.
The thicker a fluid is the more viscous. If the fluid is less viscous it is thinner. A fluid is liquid AND gas. If a fluid is hotter is gets less viscous but if it is cooler it will be more viscous.
if its viscous, it means that its very resist to flow, it will take much longer than a non-viscous liquid will such as soap compared to non-viscous water.