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

This fall, Phoenix will welcome a first-of-its-kind International Dark Sky Discovery Center, a 23,000-square-foot astronomy hub with an observatory, planetarium, and immersive exhibits. —Stephanie Vermillion, Travel + Leisure, 8 May 2025

The origin of the Lyrid meteors can be found in the constellation Lyra, and the bright star Vega in the north eastern sky, using a planetarium app like Starry Night or Stellarium. —Anthony Wood, Space.com, 23 Apr. 2025

For the most accurate location-specific information, consult online planetariums like Stellarium. —Jamie Carter, Forbes.com, 16 June 2025

In January, at an official celebration of the island’s dark-sky status, grown-ups stepped inside the mobile planetarium and explored the night sky. —Nicholas J. R. White Kat Hill, 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