thi·mer·o·sal (th?-m?r??-s?l?)n. A cream-colored crystalline powder, C9H9HgNaO2S, used as a local antiseptic for abrasions and minor cuts.[thi(o)- + mer(cury) + -o- + sal(icylate).]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.thimerosal (?a??m?r??sæl) n (Elements & Compounds) a creamy white crystalline compound of mercury, used in solution as an antiseptic. Formula: C9H9HgNaO2S[C20: from thio- + mer(cury) + sal(icylate)]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014thi?mer?o?sal (?a??m?r ??sæl, -?m?r-) n. a crystalline, water-soluble powder, C9H9HgNaO2S, used as an antiseptic. [1945?50; perhaps thi- + mer (cury) + -o- + sal (icylate)] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.