The Collaborative International Dictionary
Mediastine
Mediastine \Me`di*as"tine\, Mediastinum \Me`di*as*ti"num\, n. [NL. mediastinum, fr. L. medius middle; cf. mediastinus helper, a menial servant, LL. mediastinus equiv. to medius: cf F. m['e]diastin.] (Anat.) A partition; a septum; specifically, the folds of the pleura (and the space included between them) which divide the thorax into a right and left cavity. The space included between these folds of the pleura, called the mediastinal space, contains the heart and gives passage to the esophagus and great blood vessels.
Wiktionary
mediastine
n. (context anatomy English) mediastinum