sackcloth Syllabification: (sack·cloth)Pronunciation: /ˈsakˌklôTH, -ˌkläTH/Translate sackcloth | into Italian Definition of sackcloth noun a very coarse, rough fabric woven from flax or hemp. Phrases sackcloth and ashes used with allusion to the wearing of sackcloth and having ashes sprinkled on the head as a sign of penitence or mourning (Matt 11:21). sackcloth in other Oxford dictionaries Definition of sackcloth in the British & World English dictionary