E85 (????t?-f?v?)n. A blend of fuel that is 85 percent ethanol and 15 percent gasoline or other petroleum-based fuel.[From e(thanol).]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.