F0100900 (fī-brĭn′ə-jən)n. A protein in the blood plasma that is essential for the coagulation of blood and is converted to fibrin by the action of thrombin in the presence of ionized calcium.fi′bri·nog′e·nous(fī′brə-nŏj′ə-nəs) adj.TranslationsEncyclopediaSeefibrinogen