What is the meaning of Roundel?

Anything having a round form; a round figure; a circle.

A small circular shield, sometimes not more than a foot in diameter, used by soldiers in the fourteenth and fifteenth centuries.

A circular spot; a charge in the form of a small coloured circle.

A circular insignia painted on an aircraft to identify its nationality or service.

A bastion of a circular form.

Source: wiktionary.org

See also