Jawless fish are a unique group of aquatic animals that belong to the phylum Chordata. They lack jaws and have a mouth that is circular in shape. The term 'jawless fish' is commonly used to refer to these species, but there are also several other synonyms for the same. For instance, they are often referred to as agnathans, meaning 'no jaws' in Greek. Additionally, they are known as cyclostomes, which indicates their round-shaped mouths. Another commonly used term for jawless fish is the name 'hagfish,' which is given due to their ability to produce large amounts of slimy mucus when provoked. Regardless of what they are called, jawless fish are fascinating species that offer a unique glimpse into the evolution of aquatic life.