zi·leu·ton (z?-lo?o?tn)n. A drug that inhibits leukotriene formation, used to treat asthma.[(ben)z(oth)i(ene), one of its components + leu(ko)t(riene) + -on.]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.