n. A collection of pus within a naturally existing anatomical cavity (as opposed to an abscess, which occurs in a newly formed cavity).
the GNU version of the Collaborative International Dictionary of English
n. A collection of blood, pus, or other fluid, in some cavity of the body, especially that of the pleura.
The Century Dictionary and Cyclopedia
n. In pathology, the presence of pus in a pleural cavity; pyothorax. The word was formerly used for other purulent accumulations.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a collection of pus in a body cavity (especially in the lung cavity)
Word Usage
"Three different methods for accurately measuring breast density and associated complications, including a lung infection called empyema, increased in older children, the study found."