A circular window with mullions and tracery, generally radiating from the center, filled with stained glass.
It is so named from its fancied resemblance to a rose.
It is a beautiful characteristic of Gothic architecture in which it was developed.
At first it was placed under a round, then under a pointed arch, where soon it was inscribed in a square with spandrils.
Finally in a tier of lower windows it became the center of a vast composition.
Roses filled with glass of great beauty were used by the Lombard builders of Italy.
New Catholic Dictionary