volvelle
[vol-vel]
noun Astronomy.
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.
Origin of volvelle
1400–50; late Middle English < Medieval Latin volvella, equivalent to Latin volv(ere) to turn + -ella -elle
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Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019