This is one of the first things you scrutinize at a
wine tasting - before actually tasting any wine, but after appraising the refractive properties of the wine against the white background of a tablecloth or napkin - you give the
wine glass a little
swirl and examine how the drops on the glass' side now trickle back down to the main body of wine in the bottom of the glass. These trails are referred to as "
legs" or "
tears" and the effect is known as tearing.
The tearing of any given wine can tell you some important things about the wine before even putting any in your mouth - quick tearing indicates a relatively light body and a lower alcohol content.
As well, of course, your eyes may begin tearing up if you're about to start crying... but you already knew that.