Generally, wines are either fermented completely dry (all of the sugar in the grapes turned to alcohol) or in a semi-sweet or sweet style, where some of the sugar is left over (thus known as "residual sugar".)
The only wine I can think of that actually calls itself "partially fermented" is the 2002 Kracher Trockenbeerenauslese #12. That's an Austrian dessert "wine" made from grapes shriveled by a kind of rot, where the grapes had such a concentration of sugar, and so little water, that the winemaker was only able to get the alcohol up to 4%.
Under Austrian law, a beverage with less than 5% alcohol cannot be legally labeled as "wine". So if you look at the label of the Kracher TBA #12, you'll find that it doesn't say "wine" anywhere, but rather "partially fermented grape must".
Acesup, I'm not sure if this is what you tasted at your tasting. It's really rare and expensive stuff (about $100 for a half-bottle).