Etymology

Noun

1. Anything having a round form; a round figure; a circle.
2. A roundelay or rondelay.
   • 1595, William Shakespeare, A Midsummer Night's Dream, Act II, Scene II, line 1:

     Come, now a roundel and a fairy song ... Fairies sing.

   • Sung all the roundel lustily. — Chaucer
3. A small circular shield, sometimes not more than a foot in diameter, used by soldiers in the fourteenth and fifteenth centuries.
   • 1786, Francis Grose, A Treatise on Ancient Armour and Weapons, page 26:

     The roundel or rondache derived its name from its circular figure, it was made of oziers boards of light wood, sinews or ropes, covered with leather, plates of metal, or stuck full of nails in concentric circles or other figures.

4. : A circular spot; a charge in the form of a small coloured circle.
5. a circular insignia painted on an aircraft to identify its nationality or service.
6. A bastion of a circular form.