(medicine) Presence of air inside the pleural cavity, usually caused by injury either to the lung or the chest wall.

plural of pneumothorax

(pathology) A pulmonary condition resulting in the collection of air within the chest, which occurs absent traumatic injury. Spontaneous Pneumothorax are considered a medical emergency, generally requiring assistive radiographic evaluation to determine the extent of lung collapse, as well as determine the most appropriate course of emergency medical treatment for the patient. Abbreviated as SP.