[ at-muh s-feer-ee-uh m ]
/ ˌæt məsˈfɪər i əm /

noun, plural at·mos·pher·i·a [at-muh s-feer-ee-uh] /ˌæt məsˈfɪər i ə/.

an optical system used to simulate images of atmospheric phenomena, as cloud formations, storms, and day and night, on the inside of a dome.
a building in which this projection system is used.

Origin of atmospherium

First recorded in 1955–60; atmospher(e) + (planetar)ium Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019