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

With its curved ceiling, the 120-seat auditorium serves not just as a film and laser show venue but also as a planetarium. —Veronica Fernandez-Alvarado, Sacbee.com, 16 May 2026

The party will include a trivia challenge and short program in the planetarium and an explanation about the artifacts in the exhibit hall. —Melinda Moore, Chicago Tribune, 11 May 2026

The telescopes are weather-permitting, but either way, indoor activities including a planetarium show are also scheduled. —Jared Kaufman, Twin Cities, 23 Apr. 2026

For a dose of culture, head to the Newark Museum of Art, which boasts a planetarium and a garden along with its art collection. —Lauren Dana Ellman, Travel + Leisure, 21 Apr. 2026

Word History

First Known Use

1860, in the meaning defined at sense 1

Rhymes for planetarium

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

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