Atrium
Pronunciation : A"tri*um
Part of Speech : n.; pl. Atria.
Etymology : [L., the fore court of a Roman house.]
Definition : 1. (Arch.) (a) A square hall lighted from above, into which rooms open at one or more levels. (b) 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.
2. (Anat.)
Defn: The main part of either auricle of the heart as distinct from the auricular appendix. Also, the whole articular portion of the heart.
3. (Zo?l.)
Defn: A cavity in ascidians into which the intestine and generative ducts open, and which also receives the water from the gills. See Ascidioidea.
Source : Webster's Unabridged Dictionary, 1913