bottom fermentation

from the GNU version of the Collaborative International Dictionary of English.

• A slow alcoholic fermentation during which the yeast cells collect at the bottom of the fermenting liquid. It takes place at a temperature of 4° - 10° C. (39° - 50°F.). It is used in making lager beer and wines of low alcohol content but fine bouquet.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun brewing A slow alcoholic fermentation process carried out at low temperatures during which the yeast sinks to the bottom of the liquid. Used in brewing lager-type beers.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a slow kind of alcoholic fermentation at a temperature low enough that the yeast cells can sink to the bottom of the fermenting liquid; used in the production of lager