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

For a list of all the planetariums to visit to view the meteor showers, check out our guide. —Tiffany Acosta, AZCentral.com, 8 July 2025

The opto-mechanical planetarium projector remains a technological wonder of the modern world. —Martin Bush, Space.com, 5 July 2025

The planetarium offers presentations in English and provides transportation to and from the city center. —Carolyn Heller, Forbes.com, 19 June 2025

Moreover, for the most accurate location-specific information, refer back to online planetariums such as Stellarium. —Valerie Mesa, People.com, 21 May 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