Definition of mediastinum in US English:


nounPlural mediastina

  • A membranous partition between two body cavities or two parts of an organ, especially that between the lungs.

    • ‘A peritoneal sac protrudes through the hiatus into the mediastinum next to the esophagus.’
    • ‘The most common sites of tumor metastases are the lymph nodes in the mediastinum.’
    • ‘The left main bronchus was exposed at the posterior mediastinum and separated from connective tissue.’
    • ‘The tumor, which is often but not always associated with cystic lung lesions, may arise in pulmonary parenchyma, the mediastinum, and pleura.’
    • ‘On the lateral radiograph there appeared to be herniation of the left lung through the anterior mediastinum.’


Late Middle English: neuter of medieval Latin mediastinus ‘medial’, based on Latin medius ‘middle’.