mediastinum
noun
me·di·as·ti·num ˌmē-dē-ə-ˈstī-nəm 
plural mediastina ˌmē-dē-ə-ˈstī-nə
: the space in the chest between the pleural sacs of the lungs that contains all the tissues and organs of the chest except the lungs and pleurae
also : this space with its contents
mediastinal
ˌmē-dē-ə-ˈstī-nᵊl
adjective 
Example Sentences
Recent Examples on the Web Limited-stage disease is used to describe lung cancer that’s only found within one lung, and may be found in the mediastinum between the lungs. 
Amanda Macmillan, Health.com, 23 July 2019
Amanda Macmillan, Health.com, 23 July 2019 Word History
Etymology
New Latin, from Medieval Latin, neuter of mediastinus medial, from Latin medius
First Known Use
15th century, in the meaning defined above
Medical Definition
mediastinum
noun
me·di·as·ti·num ˌmēd-ē-ə-ˈstī-nəm
plural mediastina -nə
1
: the space in the chest between the pleural sacs of the lungs that contains all the viscera of the chest except the lungs and pleurae
also : this space with its contents
2
: mediastinum testis