nys·ta·tin (n?s?t?-t?n)n. An antibiotic, C46H77NO19, produced by the actinomycete Streptomyces noursei and used to treat fungal infections.[ N(ew) Y(ork) Stat(e Health Department Laboratory)laboratory where it was first isolated + -in.]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.nystatin (?n?st?t?n) n (Pharmacology) an antibiotic obtained from the bacterium Streptomyces noursei: used in the treatment of infections caused by certain fungi, esp Candida albicans[C20: from New York State, where it was originated + -in]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014