The Collaborative International Dictionary of English v.0.48:

black lung \black lung\ black lung disease \black lung disease\,
   n. (Med.)
   the popular name for a form of the chronic lung disease
   pneumoconiosis which is observed among coal miners, and is
   caused by the inhalation of coal dust. It is thus named
   because of the black appearance of the lungs
   (pneumomelanosis) of those affected with the disease. See
   also the related condition anthracosis.
   [PJC.]

WordNet (r) 3.0 (2006):

black lung disease
    n 1: lung disease caused by inhaling coal dust [syn:
         anthracosis, black lung, black lung disease, coal
         miner's lung]