Rāin'bōw, n.

n. [A-S. rēnboga, Ger. regenbogen.] A bow or arch exhibiting, in concentric bands, the several colors of the spectrum, and formed in the part of the hemisphere opposite to the sun by the refraction and reflection of his rays in drops of falling rain.

Besides the ordinary bow, called also primary rainbow, which is formed by two refractions and one reflection, there is also another often seen exterior to it, called the secondary rainbow, concentric with the first, and separated from it by a small interval. It is formed by two refractions and two reflections, is much fainter than the primary bow, and has its colors arranged in the reverse order to those of the latter.

Lunar rainbow, a fainter arch of the same kind, formed by the moon. — Marine rainbows, or sea-bows, similar bows seen at sea. — Supernumerary rainbow, a smaller bow, usually of red and green colors only, sometimes seen within the primary or without the secondary rainbow, and in contact with them.