Main Entry: me·di·as·ti·num

Pronunciation: \ˌmē-dē-ə-ˈstī-nəm\

Function: noun

Inflected Form(s): plural me·di·as·ti·na \-nə\

Etymology: New Latin, from Medieval Latin, neuter of mediastinus medial, from Latin medius

Date: 1541

: 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

— me·di·as·ti·nal \-ˈstī-n^əl\ adjective