A bow or arch exhibiting, in concentric bands, the several colours of the spectrum, and formed in the part of the hemisphere opposite to the sun by the refraction and reflection of the sun's 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 colours arranged in the reverse order from those of the latter. Lunar rainbow, a fainter arch or rainbow, formed by the moon. Marine rainbow, or sea bow, a similar bow seen in the spray of waves at sea.
(Science: zoology) Rainbow trout See wrasse. Supernumerary rainbow, a smaller bow, usually of red and green colours only, sometimes seen within the primary or without the secondary rainbow, and in contact with them.
Origin: AS. Regenboga, akin to G. Regenbogen. See Rain, and Bow anything bent.