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 the most accurate location-specific information, consult Stellarium and other online planetariums. —Jamie Carter, Forbes.com, 19 Jan. 2026

The planetarium, located in the Jenks High School Math and Science building, includes a 50-foot-high SciDome, classes and talks on astronomy and individual telescopes. —Isa Almeida, Oklahoman, 15 Jan. 2026

Construction has already begun on an expansion, with the work slated to include a state-of-the-art digital planetarium and event venue for speaking engagements and workshops. —Lauren Breedlove, Travel + Leisure, 10 Jan. 2026

From the Snow King Mountain ski resort, a scenic gondola ride whisks you to state-of-the-art planetarium, where the wonders of the cosmos come to life. —Josh Roberts, USA Today, 8 Jan. 2026

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