noun ·Rare ·Advanced level

Definitions

Noun

1. 1
   The region in mammals between the pleural sacs, containing the heart and all of the thoracic viscera except the lungs.
2. 2
   the part of the thoracic cavity between the lungs that contains the heart and aorta and esophagus and trachea and thymus wordnet

Etymology

From New Latin mediastīnum, from Medieval Latin mediastīnus (“middling; middle”), from Latin mediastīnus (“a common servant”).

Related phrases

pleural sac

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.