Top fermentation. An alcoholic fermentation during which the yeast cells are carried to the top of the fermenting liquid. It proceeds with some violence and requires a temperature of 14-30° C. (58-86° F.). It is used in the production of ale, porter, etc., and of wines high in alcohol, and in distilling.
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 top fermentation
      n : a violent kind of alcoholic fermentation at a temperature
          high enough to carry the yeast cells to the top of the
          fermenting liquid; used in the production of ale; "top
          fermentation uses a yeast that ferments at higher
          temperatures than that used for bottom fermentation"