- (n.) A square hall lighted from above, into which rooms open at one or more levels.
- (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.) 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.) 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 cavity, entrance or passage; as, the atrium or atrial cavity, in the body wall of the amphioxus; an atrium of the infundibula of the lungs, etc.
Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). atrium. Retrieved September 20, 2026, from http://smartdefine.org/atrium/definitions/1976870 |
| Chicago | Webster's. 2011. "atrium" http://smartdefine.org/atrium/definitions/1976870 (accessed September 20, 2026). |
| Harvard | Webster's 2011, atrium, Smart Define, viewed 20 September, 2026, <http://smartdefine.org/atrium/definitions/1976870>. |
| MLA | Webster's. "atrium" 27 May 2011. Web. 20 September 2026. <http://smartdefine.org/atrium/definitions/1976870> |