What's the difference between rondel and roundlet?
Rondel
Definition:
(n.) A small round tower erected at the foot of a bastion.
(n.) Same as Rondeau.
(n.) Specifically, a particular form of rondeau containing fourteen lines in two rhymes, the refrain being a repetition of the first and second lines as the seventh and eighth, and again as the thirteenth and fourteenth.