The word "mytilid" refers to a type of marine bivalve mollusk commonly known as mussels. When describing mussels, there are several synonyms that can be used interchangeably with mytilid. These may include terms like shellfish, marine mollusk, bivalve, or even simply "mussel". Other related synonyms could include marine invertebrate, filter feeder, or even seafood. No matter what term is used, they all refer to this delicious and nutritious contribution to our culinary world that has been enjoyed for centuries.