Thrombin is a crucial enzyme responsible for blood clotting, and there are some synonyms that can be used to refer to it. One possible alternative term is Coagulation Factor II, which can be seen in some scientific literature. Another synonymous term is thrombase, which is derived from the thrombin base. The protein known as serine protease 2 or F2 is also a synonym for thrombin. Some people may use the term blood clotting factor II or thrombin-cleaved fibrinogen B beta chain when discussing thrombin. Overall, although thrombin is the most commonly used term to refer to this enzyme, there are several synonyms that can be used interchangeably.