rondelle

[ron-del]

noun

a small disk of glass used as an ornament in a stained-glass window.
Jewelry. a flat bead, often of rock crystal or onyx, used in a necklace as a spacer between contrasting stones.

Origin of rondelle

From French, dating back to 1830–40; see origin at rondel

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Rondelle, ron-del′, n. anything round: one of the successive crusts formed on molten metal when cooling, a rosette.
Chambers's Twentieth Century Dictionary (part 3 of 4: N-R)
Various