Cookbook:Rolling Boil

A rolling boil (also roiling boil) is when a liquid is boiled rapidly with lots of bubbling. This requires much more energy than simmering, and is often discouraged because it can break up or alter the shape of ingredients, whereas simmering will keep the ingredients whole.

Some recipes require a rolling boil for the entire cooking period. Typically, however, recipes will specify that the liquid is brought to a rolling boil, then reduced to a simmer for the remainder of the cooking period.