What does Slub mean?

Refers to any inconsistencies that are prevalent in denim produced on vintage shuttle looms.

Heddels explains Slub

Slubs are areas in a length of yarn than are abnormally thick due to uneven spinning. Once considered flaws, slubs are now sometimes purposely added to yarns to give the finished woven material more character.

Fabric made from slub yarn is referred to as slubby. See “Slub, Slubby, Slubbiness – Huh?” for more information.

Additional Resources

Uneven yarn which leads to slubbiness: