Fibrinous pneumonia is a medical condition where the lungs become inflamed due to the accumulation of fibrin, which is a protein that helps in blood clotting. Synonyms for fibrinous pneumonia include lobar pneumonia, croupous pneumonia, and pneumococcal pneumonia. Lobar pneumonia refers to pneumonia that occurs in one or more lobar, or large, sections of the lungs, while croupous pneumonia describes pneumonia that leads to a buildup of thick fluids in the lungs. Pneumococcal pneumonia is caused by the bacterium Streptococcus pneumoniae and is the most common type of pneumonia. Other synonyms for fibrinous pneumonia include pneumonic plague and legionnaire's disease, both of which can also lead to the accumulation of fibrin in the lungs.