A commercial preparation consisting of dried cells of one or more strains of the fungus Saccharomyces cerevisiae, used as a leavening in baking.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.