zy·mase (z??m?s?, -m?z?)n. A complex of enzymes that catalyzes alcoholic fermentation in yeast, converting sugars into ethanol and carbon dioxide.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.zymase (?za?me?s) n (Biochemistry) biochem a mixture of enzymes that is obtained as an extract from yeast and causes fermentation in sugarsCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014