Rockling is a term used to describe a type of fish often found in rocky coastal areas. However, there are several other terms that can be used as synonyms for rockling, including billet, bullrout, clingfish, fatherlasher, and pogge. These fish are often small and slender, with elongated bodies and spiky fins. They can be found in both saltwater and freshwater environments, and are popular as a food source in many parts of the world. While the term rockling is commonly used, it's always good to have alternative words to use in order to add variety and interest to your writing or conversations about fish.