1. roundel - Noun
2. roundel - Adjective
A rondelay.
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 sharge in the form of a small circle.
Source: Webster's dictionaryAs a child, during the war, I drew Spitfires and Messerschmitts. With Spot, I found that I had designed a fuselage! His spot is on his side, the roundel marking of an English fighter plane, and the color bar of his tail is the color stripes of a plane's rudder. Eric Hill
a hollow roundel Source: Internet
Also visible, to the right of the USAF roundel, is a radar reflector that is usually installed when not on combat operations. Source: Internet
Luxembourg roundel A NATO E-3 with the roundel of Luxembourg painted on its tail. Source: Internet
Ever since the TARDIS was redesigned at the beginning of the 2010 series, there have been a range of different roundel designs around the console room. Source: Internet
It was carried on a prominent white roundel on each sponson, underneath an infinity symbol. Source: Internet