Mandorla

A mandorla is an aureola, usually in the shape of a vesica piscis, which surrounds the figures of Christ and the Virgin Mary in traditional Christian art. It is distinguished from a halo in that it encircles the entire body, and not just the head. It is commonly used to frame the figure of Christ in Majesty in early medieval and Romanesque art, as well as Byzantine art of the same periods.

The term mandorla, from the Italian language name for the "almond" nut, refers to the usual shape. Sometimes however, especially in earlier depictions, the mandorla takes circular or elliptical forms. Sometimes, also usually in earlier forms, the mandorla is shown as the intersection of two circles. Rhombic mandorlas are also sometimes seen.

In icons of the Eastern Orthodox Church, the mandorla is used to depict sacred moments which transcend time and space, such as the Resurrection and the Transfiguration of Christ and the Dormition of the Theotokos. These mandorla will often be painted in several concentric patterns of color which grow darker as they come close to the center. This is in keeping with the church's use of apophatic theology, as described by Dionysius the Areopagite and others. As holiness increases, there is no way to depict its brightness except by darkness.

In architectural iconography, the frame of the mandorla is often marked with decorative mouldings. The interior of the mandorla is usually undecorated, but may contain the symbols Α and Ω or, less frequently, depictions of a starry sky or clouds.

...
Wikipedia