Wine is the juice of fermented grapes. 

-The University Wine Course by Marian W. Baldy, PH.D.

A beverage made of the fermented juice of any of various kinds of grapes, usually containing from 10 to 15 percent alcohol by volume.
-Yahoo

An alcoholic beverage made from the fermentation of grape juice.  The natural chemical balance of grapes is such that they can ferment without the addition of sugars, acids, enzymes, or other nutrients. 

-Wikipedia

The alcoholic fermented juice of fresh grapes used as a beverage. 

-Merriam-Webster Dictionary

The fermented juice of grapes, made in many varieties, such as red, white, sweet, dry, still, and sparkling, for use as a beverage, in cooking, in religious rites, etc., and usually having an alcoholic content of 14% or less. 

-Dictionary.com