phlegm

Concise Oxford English Dictionary © 2008 Oxford University Press:
phlegm /flɛm/

▶noun

• 1 the thick viscous substance secreted by the mucous membranes of the respiratory passages, especially when produced in excessive quantities during a cold.

• 2 (in medieval science and medicine) one of the four bodily humours, believed to be associated with a calm or apathetic temperament.

  ■ calmness of temperament.

– derivatives
phlegmy adjective.

– origin ME fleem, fleume, from OFr. fleume, from late L. phlegma ‘clammy moisture (of the body)’, from Gk phlegma ‘inflammation’, from phlegein ‘to burn’.