volvelle

American  

[vol-vel] / ˈvɒl vɛl /

noun

Astronomy.

1. a medieval instrument consisting of a series of concentric rotating disks, used to compute the phases of the moon and its position in relation to that of the sun.

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Etymology

Origin of volvelle

1400–50; late Middle English < Medieval Latin volvella, equivalent to Latin volv ( ere ) to turn + -ella -elle

Example Sentences

At the Morgan, the book is opened to a fanciful volvelle in which a green dragon with orange wings, representing the constellation Drago, serves as a pointer to indicate lunar and solar eclipses.

From New York Times • Jun. 12, 2014

The lunar phase volvelle can be seen through the circular opening at the back of the astrolabe.

From On the Origin of Clockwork, Perpetual Motion Devices, and the Compass by Price, Derek J. de Solla (Derek John de Solla)