Definition - What does Grosslage mean?
Grosslage is a German classification that is used to describe a type of large collective vineyard that is comprised of many smaller vineyards that all use the same name. The vineyards within a Grosslage are called Einzellage (single vineyards) and usually have the name of their village along with Grosslage or Einzellagen, which denotes that they are part of a larger collective.
WineFrog explains Grosslage
The size of Grosslagen can have a large variance from 125 acres to over 5,000 and can have any number of smaller vineyards and villages within them. They typically all produce wine of a similar style like reds or whites and the fruit is also of similar species or varietal. This is just a way that Germany classifies wines starting after a law was created in 1971.
An example of this are the Einzellagen of the German town Kiedrich, which are five different vineyards (Klosterberg, Graefenberg, Klosterberg, Wasseros, Sandgrub) that make up a Grosslage from Kiedrich named Heiligenstock.
The grosslagen can have their own specific name or can just label their wines with the grosslage from a certain town or region. It is usually the second name on the bottle that is the specific name of the grosslage which means several different vineyards within one area.