volvelle

[ vol-vel ]

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.

Word History and Origins

Origin of volvelle¹

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

Example Sentences

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

From Project Gutenberg