Definitions
1.nounAnything having a round form; a round figure; a circle."the London Underground roundel"
2.nounA roundelay or rondelay.
3.nounA small circular shield, sometimes not more than a foot in diameter, used by soldiers in the fourteenth and fifteenth centuries.
4.nounA circular spot; a charge in the form of a small coloured circle.
5.nounA circular insignia painted on an aircraft to identify its nationality or service.
6.nounA bastion of a circular form.