A coarse cloth of goat or camel’s hair or of flax, hemp, or cotton. (Merriam – Webster)
A garment of sackcloth worn as a sign of mourning or penitence. (Merriam – Webster)
The thick, rough material used to make sacks (=large strong bags)
Sackcloth is rough woven material that is used to make sacks. (Collins Dictionary)
If you talk about sackcloth or sackcloth and ashes you are reffering to an exaggerated attempt by someone to show that they are sorry for doing something wrong. (Collins Dictionary)
A very coarse, rough fabric woven from flax or hemp. (Oxford Dictionaries)
Close up of sackcloth, stock photo. Colourbox.