Noun
An albuminous substance existing in the blood, and in other animal fluids, which either alone or with fibrinoplastin or paraglobulin forms fibrin, and thus causes coagulation.
Source: Webster's dictionaryFibrinogen Antigen, Nephelometry Fibrinogen is a plasma glycoprotein that can be transformed into a fibrin clot in response to vascular or tissue injury. Source: Internet