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

Craft a miniature to add to Adam’s model town of Winter River, Connecticut, see ghosts at a science show, investigate sandworms on Titan, or visit Betelgeuse in the planetarium. — John Coffren, Baltimore Sun, 24 Sep. 2026

Her parents, who met at a planetarium, are in the crowd at Dye Creek. — Sean MacAday, Sacbee.com, 19 Sep. 2026

Last November, his latest play became the first in the world to be staged in a planetarium. — Maddie Connors, Los Angeles Times, 15 Sep. 2026

Although there are plenty of books in three languages (Arabic, French, and English), there are also museums, a planetarium, and a lab dedicated to restoring and preserving ancient manuscripts. — Condé Nast, Condé Nast Traveler, 7 Sep. 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