Rain"bow` (-bō`), n. [AS.
regenboga, akin to G. regenbogen. See Rain, and
Bow anything bent.] 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 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 colors
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. -- Rainbow trout
(Zoöl.), a bright-colored trout (Salmo
irideus), native of the mountains of California, but now
extensively introduced into the Eastern States, Japan, and other
countries; -- called also brook trout, mountain trout,
and golden trout. -- Rainbow wrasse.
(Zoöl.) See under Wrasse. --
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.