An inorganic fibrous substance that is produced by steam blasting and cooling molten glass or a similar substance and is used as an insulator and a filtering material. Also called rock wool.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.