From Dick Blick Art Materials - find spray and brush-on varnishes that suit every fine art and craft need, for paintings, drawings, sign-making, screen-printing, and more.
http://www.dickblick.com/categories/varnishes/

Varnishes are also applied over wood stains as a final step to achieve a film for gloss and protection. Some products are marketed as a combined stain and varnish.
http://en.wikipedia.org/wiki/Varnish

varnish, homogeneous solution of gum or of natural or synthetic resins in oil (oil varnish) or in a volatile solvent (spirit varnish), which dries on exposure to air, forming a ...
http://encyclopedia2.thefreedictionary.com/varnishes

Varnishes are final coatings which protect finished pictures from the build up of dirt and grease. Oil paintings must be thoroughly dry (at least 6 -12 months) before varnishing.
http://www.winsornewton.com/products.aspx?PageID=300

varnish (vär´nish), n (cavity liner, cavity varnish), a clear solution of resinous material or natural gum, such as copal or rosin dissolved in acetone, ether, or chloroform ...
http://medical-dictionary.thefreedictionary.com/varnishes