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

There are several activities on the docket, including a slime bar, temporary tattoos, dinosaur excavation, bubble area, live doodle booth, mobile noble planetarium and more. —Brayden Garcia, Fort Worth Star-Telegram, 3 Mar. 2026

For museum lovers, the California Academy of Sciences is a must-visit that combines marine life, planetarium shows, and a tropical rainforest biome under one roof. —Iona Brannon, Travel + Leisure, 15 Feb. 2026

For the most accurate location-specific information, consult Stellarium and other online planetariums. —Jamie Carter, Forbes.com, 30 Jan. 2026

The center has planetarium shows most Fridays and sometimes offers simulated space missions to the public. —Brandon Lingle, San Antonio Express-News, 28 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