planetarium

noun

plan·​e·​tar·​i·​um ˌpla-nə-ˈter-ē-əm 

plural planetariums or planetaria ˌpla-nə-ˈter-ē-ə 

1

: a model or representation of the solar system

2

a

: an optical device for projecting various celestial images and effects

b

: a building or room housing such a projector

Examples of planetarium in a Sentence

Recent Examples on the Web

The Adler Planetarium opened in 1930 as the first planetarium in the U.S., and is still a leading center for public space science education. —Iona Brannon, Travel + Leisure, 8 Nov. 2025

The planetarium is school, theater, and cinema in one classroom under the eternal dome of the sky. —Caroline A. Jones, Artforum, 1 Nov. 2025

Oahu’s Bishop Museum has a planetarium specifically set up to teach celestial navigation. —Literary Hub, 21 Oct. 2025

And Blazy’s childhood planetarium. —Nathan Heller, Vogue, 14 Oct. 2025

Word History

First Known Use

1860, in the meaning defined at sense 1

Rhymes for planetarium

• honorarium
• sanitarium
• aquarium
• herbarium
• ovarium
• puparium
• samarium
• zoarium
• armamentarium
• cerium

Kids Definition

planetarium

noun

plan·​e·​tar·​i·​um ˌplan-ə-ˈter-ē-əm 

plural planetariums or planetaria -ē-ə 

1

: a device that projects images of heavenly bodies on a ceiling shaped like a dome

2

: a building or room housing a planetarium