volvelle
noun
vol·velle
variants:
or less commonly volvell \ ˈvälˌvel \
plural -s
Definition of volvelle
: an old contrivance for ascertaining the time of the rising and setting of the moon and sun and the time of high and low tide consisting of one or more movable circles with pointers and figures of the moon and sun which are placed upon several graduated and figured circles drawn on the leaf of a book
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