Thi·o·kol (th???-kôl?, -k?l?, -k?l?) A trademark for any of various polysulfide polymers in the form of liquids, water dispersions, and rubbers used in seals and sealants.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.Thi?o?kol (??a? ??k?l, -?k?l) Trademark. a synthetic rubber product derived from an organic halide and an alkaline polysulfide: used chiefly in making sealants, adhesives, and hoses for gasoline and oil. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.