\Fi"brin\, n. [Cf. F. fibrine. See {Fiber}.] (Physiol.
Chem.)
1. A white, albuminous, fibrous substance, formed in the
   coagulation of the blood either by decomposition of
   fibrinogen, or from the union of fibrinogen and
   paraglobulin which exist separately in the blood. It is
   insoluble in water, but is readily digestible in gastric
   and pancreatic juice.
2. The white, albuminous mass remaining after washing lean
   beef or other meat with water until all coloring matter is
   removed; the fibrous portion of the muscle tissue; flesh
   fibrin.
3. An albuminous body, resembling animal fibrin in
   composition, found in cereal grains and similar seeds;
   vegetable fibrin.
{Fibrin factors} (Physiol.), the albuminous bodies,
   paraglobulin and fibrinigen in the blood, which, by the
   action of the fibrin ferment, are changed into fibrin, in
   coagulation.
{Fibrin ferment} (Physiol. Chem.), a ferment which makes its
   appearance in the blood shortly after it is shed, and is
   supposed to be the active agent in causing coagulation of
   the blood, with formation of fibrin.