(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)
The Collaborative International Dictionary of English (GCIDE) v.0.53Collaborative International Dictionary (GCIDE)
n. [ Gr. &unr_; air + E. thorax. ] (Med.) A condition in which air or other gas is present in the cavity of the chest; -- called also pneumatothorax. [ 1913 Webster ]