clotting factor

Coagulation is a complex process by which blood forms solid clots. It is an important part of hemostasis (the cessation of blood loss from a damaged vessel) whereby a damaged blood vessel wall is covered by a platelet- and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel. Disorders of coagulation can lead to an increased risk of bleeding and/or clotting and embolism.
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Clot·ting factor n. Any of various plasma components involved in the clotting of blood, including fibrinogen, prothrombin, thromboplastin, and [more]Clotting factor - Community and Resources

Noun
1. any of the factors in the blood whose actions are essential for blood coagulation
(synonym) coagulation factor
(hypernym) plasma protein
(hyponym) fibrinogen, factor I

Any of a group of chemical blood constituents whose interaction causes blood coagulation.