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

Those who vacation here can explore the preserve at Bird Island and visit the planetarium. —Brandee Gruener, Southern Living, 9 Sep. 2025

That is followed by a tabletop planetarium featuring images of planets beamed onto moving objects which magically protrude from it. —Caroline Reid, Forbes.com, 8 Sep. 2025

Home planetariums are often dome or round-shaped and offer more than just lasers making out to be stars on a wall and they can definitely be used as STEM and learning tools. —Alexander Cox, Space.com, 3 Sep. 2025

In 2024 Lowell Observatory expanded with the Astronomy Discovery Center, which has a multistory LED theater called the Lowell Universe Theater, hands-on activities including the Orbits Curiosity Zone and an open sky planetarium. —Michael Salerno, AZCentral.com, 26 Aug. 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