sputum bloody sputum A sputum that is characterized by blood or bloody mucus discharged from the air passages caused by common forms of infection in the lungs and airways, such as acute bronchitis or pneumonia. Bloody sputum can also come from cancer of the lung. Bloody sputum (spitting up blood or bloody mucus) can come from common forms of infection in the lungs and airways, such as acute bronchitis or pneumonia. Bloody sputum can also come from cancer of the lung. symptoms SYMP:0000447