What is slub?

A slub is a term used in textiles to describe a thick or irregular section in a yarn or fabric. It is caused by variations in the thickness of the fibers or uneven spinning. Slubs can add texture and interest to fabrics and are often intentionally created in high-end fashion fabrics. They are commonly found in natural fibers such as cotton, linen, and silk, but can also be found in synthetic fibers. Slubbed fabrics are often used in casual clothing such as t-shirts, sweatshirts, and denim.