fibrin Syllabification: (fi·brin)Pronunciation: /ˈfībrən/Definition of fibrin noun Biochemistry an insoluble protein formed from fibrinogen during the clotting of blood. It forms a fibrous mesh that impedes the flow of blood. Derivatives fibrinoidPronunciation: /ˈfībrəˌnoid, ˈfib-/ adjective fibrinousPronunciation: /ˈfībrənəs, ˈfib-/ adjective Origin: early 19th century: from fiber + -in1fibrin in other Oxford dictionaries Definition of fibrin in the British & World English dictionary