Definition of atrium

• n. - A square hall lighted from above, into which rooms open at one or more levels.
• n. - An open court with a porch or gallery around three or more sides; especially at the entrance of a basilica or other church. The name was extended in the Middle Ages to the open churchyard or cemetery.
• n. - The main part of either auricle of the heart as distinct from the auricular appendix. Also, the whole articular portion of the heart.
• n. - A cavity in ascidians into which the intestine and generative ducts open, and which also receives the water from the gills. See Ascidioidea.
• n. - A square hall lighted from above, into which rooms open at one or more levels.
• n. - An open court with a porch or gallery around three or more sides; especially at the entrance of a basilica or other church. The name was extended in the Middle Ages to the open churchyard or cemetery.
• n. - The main part of either auricle of the heart as distinct from the auricular appendix. Also, the whole articular portion of the heart.
• n. - A cavity in ascidians into which the intestine and generative ducts open, and which also receives the water from the gills. See Ascidioidea.