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 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

Download the virtual planetarium stargazing app Star Walk to help locate it. —Skyler Caruso, People.com, 8 Apr. 2025

This is one of the few institutions worldwide to have both an aquarium and a planetarium in one museum. —Alesa Andrew, Parents, 27 Mar. 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