A rough cloth of camel's hair, goat hair, hemp, cotton, or flax. (noun)
Garments made of this cloth, worn as a symbol of mourning or penitence. (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.
Use "sackcloth" in a sentence
"Clothed in sackcloth and ashes, they are continuing their work of expiation."
"What would be the point of covering myself in sackcloth and ashes?"
"In my view, the Deputy Chief should have been round to the house in sackcloth on bended knee, apologising in person for such a crass move."