Rousing is an expression used for processes bringing yeast into homogenous suspension in either wort or beer to render the yeast more active with respect to its fermentation performance. Traditionally, the term refers to procedures that are used to prepare the pitching yeast for actual pitching. In the absence of modern techniques for effective, in-line pitching of the yeast homogenously into large volumes of wort, such preparation of the yeast may be necessary to ensure short, complete, and consistent fermentations. In practice, rousing may be performed by pumping or pouring the yeast from one vessel to another, by mechanically agitating the yeast, or by blowing sterile air, oxygen, or CO₂ into the bottom of the yeast-holding vessel.

Rousing may also refer to the process of “revitalizing” yeast that has flocculated and settled to the bottom of the fermentation vessel before the fermentation is complete or before sufficient diacetyl reduction has been achieved. Such yeast may be brought back into suspension in the beer, normally by injecting CO₂—or in rare cases compressed air—into the bottom of the vessel. If this is not sufficiently effective, some breweries will recirculate the entire contents of the fermenting vessel to resuspend all of the yeast in an attempt to “rouse” it from an inactive state.