atrium

Concise Oxford English Dictionary © 2008 Oxford University Press:
atrium /ˈeɪtrɪəm/

▶noun (pl. atria /ˈeɪtrɪə/ or atriums)

• 1 Architecture an open-roofed central court in an ancient Roman house.

  ■ a central hall or court in a modern building, typically rising through several stories and having a glazed roof.

• 2 Anatomy each of the two upper cavities of the heart from which blood is passed to the ventricles.

– derivatives
atrial adjective.

– origin C16: from L.