a. An arc of spectral colors, usually identified as red, orange, yellow, green, blue, indigo, and violet, that appears in the sky opposite the sun as a result of the refractive dispersion of sunlight in drops of rain or mist.
b. A similar arc or band, as one produced by a prism or by iridescence.
c. A graded display of colors.
2. An illusory hope: chasing the rainbow of overnight success.
3. A diverse assortment or collection.
[Middle English, from Old English rēnboga : rēn, rain + boga, bow; see BOW3.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.