ke·to·co·na·zole (k??t?-k?-n??z?l?)n. A broad-spectrum antifungal agent, C26H28Cl2N4O4, administered as a topical treatment or as a second-line oral treatment for a variety of fungal infections.[keto(ne) + (mi)conazole.]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.