Phlegm

noun

1. One of the four humors making up the body in ancient and mediaeval medicine; said to be cold and moist, and often identified with mucus.
2. Viscid mucus produced by the body, later especially mucus expelled from the bronchial passages by coughing.
3. A watery distillation, especially one obtained from plant matter; an aqueous solution.
4. Calmness of temperament, composure; also seen negatively, sluggishness, indifference.