Definition of tae kwon do for English Language Learners. : a style of fighting that originated in Korea and that uses kicks and punches but no weapons. Britannica.com: Encyclopedia article about tae kwon do.
It is also used in the baking process as a leavening agent; yeast releasing gas into their environment results in the spongy-like texture of breads and cakes. Because of its role in fermentation, humans have known about and used Saccharomyces cerevisiae for a long time.
brewer's yeast-yeast used in fermenting beer. leaven, leavening-a substance used to produce fermentation in dough or a liquid. mother-a stringy slimy substance consisting of yeast cells and bacteria; forms during fermentation and is added to cider or wine to produce vinegar.