The word "ribbed" has multiple meanings, depending on its context.
1) In textiles and clothing, ribbing refers to a pattern of knit or crocheted stitches that create vertical ridges in fabric. Ribbed materials are often used for making t-shirts, socks, and other garments because they provide structure and elasticity.
2) In anatomy, the term "rib" refers to one of a set of 12 bones on each side of the human body that connects the spine to the shoulder blade and arm. These bones are curved and have ridges running down their length, which is where the word "ribbed" comes from in this context.
3) In architecture or engineering, ribbed refers to a type of structure with an ornamental pattern formed by diagonal struts or moldings that run between two main horizontal members. This design element can be found in many historical buildings and structures such as cathedrals and bridges.