a fibrous, insoluble blood protein: in the clotting process, thrombin converts fibrinogen to fibrin monomers which polymerize to form clots
Origin:
fibr(e) + -in
See fibrin in American Heritage Dictionary 4
noun
An elastic, insoluble, whitish protein produced by the action of thrombin on fibrinogen and forming an interlacing fibrous network in the coagulation of blood.