Definition of "planisphere" [plan•i•sphere]

• A representation of a sphere or part of a sphere on a plane surface. (noun)
• Astronomy A polar projection of half or more of the celestial sphere on a chart equipped with an adjustable overlay to show the stars visible at a particular time and place. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "A planisphere is a visual aid to astronomers and stargazers."
• "A planisphere is a small thing that I can just leave tucked in with my maps in my car and anytime I'm out doing a star party or I'm at a friend's for a barbeque and they're like, "hey, what's that object?""
• ""planisphere," because it can be made to show all the constellations visible at a given time at a given date, and no others."