Dictionary.net

Any bacterial component or product which causes coagulation in plasma containing an anticoagulant such as citrate, heparin or oxalate. Coagulases are produced by certain staphylococci and by Yersinia pestis. Staphylococci produce two types of coagulase: Staphylocoagulase, a free coagulase that produces true clotting of plasma, and Staphylococcal clumping factor, a bound coagulase in the cell wall that induces clumping of cells in the presence of fibrinogen. (Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2nd ed)