The American Heritage® Dictionary of the English Language, 4th Edition
n. Accumulation of air or gas in the pleural cavity, occurring as a result of disease or injury, or sometimes induced to collapse the lung in the treatment of tuberculosis and other lung diseases.
n. Presence of air inside the pleural cavity, usually caused by injury either to the lung or the chest wall.
the GNU version of the Collaborative International Dictionary of English
n. A condition in which air or other gas is present in the cavity of the chest; -- called also pneumatothorax.
The Century Dictionary and Cyclopedia
n. The presence of air in the pleural cavity. Also pneumatothorax.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. abnormal presence of air in the pleural cavity resulting in the collapse of the lung; may be spontaneous (due to injury to the chest) or induced (as a treatment for tuberculosis)
Word Usage
"This condition is known as pneumothorax and may result in collapse of the lung."