The Collaborative International Dictionary of English v.0.48:
Hemothorax \Hem`o*tho"rax\, n. [NL. See Hemo-, and Thorax.] (Med.) An effusion of blood into the cavity of the pleura. [1913 Webster]WordNet (r) 3.0 (2006):
hemothorax n 1: accumulation of blood in the pleural cavity (the space between the lungs and the walls of the chest) [syn: hemothorax, haemothorax]