Empyema
Empyema , noun
[New Latin, from Greek {not transcribed}, from {not transcribed} to suppurate; {not transcribed} in + {not transcribed} pus.]
(Medicine) A collection of blood, pus, or other fluid, in some cavity of the body, especially that of the pleura. — Dunglison
The term empyema is now restricted to a collection of pus in the cavity of the pleura.