A spontaneous-fermented unblended ale that is indigenous to the Senne Valley of Belgium, a large portion of wheat brings out the crispness though the flavor is dominated with a unique tartness from the wild yeast and bacteria that inoculate the brew from both airborne and tainted barrels that they ferment in. Light bodied with little hop flavor or bitterness. Look for hard cider, white wine or similar tartness. Lambics are aged before consumption to ensure that the tartness has mellowed.
In the case of Fruit Lambics, whole fruits are traditionally added after spontaneous fermentation has started. Kriek (cherries), Frambroise (raspberries), Peche (peach) and Cassis (black currant) are common fruits, all producing subtle to intense fruit characters respectively. Once the fruit is added, the beer is subjected to additional maturation before bottling. Malt and hop characters are generally low to allow the fruit to consume the palate. Alcohol content tends to be low.
A geuze is a traditional Belgian blend of young and old Lambics, which are bottled after blending, then aged for 2-3 years to produce a dryer, fruitier and more intense style of Lambic. There is no hop character, some are filtered and force carbonated if not pasteurized as well. Some say that this is the more harsh lambic as the sourness is pretty intense. (BeerAdvocate)