(Science: anatomy) a chamber, used in anatomical nomenclature to designate a chamber affording entrance to another structure or organ. Usually used alone to designate an atrium of the heart.
Origin: L., gr. Atrion = hall
Any chamber that is connected to other chambers or passageways (especially one of the two upper chambers of the heart).The central area in a building; open to the sky.A chamber found in the heart that receives deoxygenated blood from the body.