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1. The liquid, usually either naturally soured or cultured with acid-producing bacteria, that remains after the butterfat has been removed from cream by churning.
2. A sour milk made by culturing usually skim milk with acid-producing bacteria.
(Cookery) the sourish liquid remaining after the butter has been separated from milk, often used for making scones and soda bread
1. the acidulous liquid remaining after butter has been separated from milk or cream.
2. a similar liquid made by adding a bacterial culture to whole or skim milk.
Originally, the liquid remaining after butter churning. Since butter is no longer mostly made at home, buttermilk is usually bought, and is directly made by the addition of an appropriate bacteria to sweet milk.