Definition of atrium
noun (plural atria /ˈātrēə/ 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 receives oxygenated blood from the pulmonary vein. Also called auricle.
late 16th century: from Latin