par·a·ben (p?r??-b?n?)n. Any of various esters of para-hydroxybenzoic acid that have bactericidal or fungicidal properties and are therefore used as preservatives in cosmetics and pharmaceuticals.[para(-hydroxy)ben(zoic acid).]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.paraben (?pær??b?n) n (Chemistry) any ester of parahydroxybenzoic acid, some of which are used in cosmetics and pharmaceuticals and have been found in breast cancer tumoursCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014