Literally "half dry". It's not dry, but it isn't really sweet either.
The term halbtrocken is regulated by the German wine law. A wine can be labeled halbtrocken if it exceeds the maximum values declared for trocken wines.
A wine labeled halbtrocken can either have:
- a maximum of 12 g/l of residual sugar
- a maximum of 18 g/l of residual sugar if the acidity level expressed in g/l is not more than 10 g/l less than the residual sugar (e.g. if a wine has 14 g/l residual sugar and the acidity is 4 g/l, then it is still dry. If the acidity level were 3.9 g/l this wine could no longer be called halbtrocken).
See also: trocken.