an arc of colored light in the sky caused by refraction of the sun's rays by rain
source: WordNet 3.0
an illusory hope
Chasing rainbows.
source: WordNet 3.0
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.
