noun (plural atria /ˈeɪtrɪə/ or atriums)
- 2 Anatomy each of the two upper cavities of the heart from which blood is passed to the ventricles. The right atrium receives deoxygenated blood from the veins of the body, the left atrium oxygenated blood from the pulmonary vein. Also called auricle.
late 16th century: from Latin