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 city is about 20 miles from Youngstown, Ohio, which has several museums, a performing arts center, a planetarium, a casino, and a horse-racing track. —Travel + Leisure Editors, Travel + Leisure, 11 Mar. 2025

How to find the 'Blaze Star' using a telescope Most astronomy and planetarium software programs and apps have T CrB in their catalogs, including Stellarium. —Jamie Carter, Space.com, 2 Mar. 2025

For the most accurate location-specific information, consult online planetariums like Stellarium. —Jamie Carter, Forbes.com, 28 Apr. 2025

The room filled with sounds that resembled the wait music for a planetarium. —Julia Whelan Emma Kehlbeck Joel Thibodeau, New York Times, 24 Feb. 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