What is "rayonnant"

Rayonnant \Ray"on*nant\ (r[=a]"[o^]n*n[a^]nt), a. [F.] (Her.) Darting forth rays, as the sun when it shines out.

a. (context heraldry English) Darting forth rays like those of the sun.

In French Gothic architecture, Rayonnant was the period between c. 1240 and 1350, characterized by a shift in focus away from the High Gothic mode of utilizing great scale and spatial rationalism (such as with buildings like Chartres Cathedral or the nave of Amiens Cathedral) towards a greater concern for two dimensional surfaces and the repetition of decorative motifs at different scales. After the mid-14th century, Rayonnant gradually evolved into the Late Gothic Flamboyant style, though as usual with such arbitrary stylistic labels, the point of transition is not clearly defined.