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• rainbow
  rainbow

  noun

  a bow or arc of prismatic colors appearing in the heavens opposite the sun and caused by the refraction and reflection of the sun's rays in drops of rain.
• Rainbow
  Rainbow

  noun

  a member of the Rainbow Guides, the youngest group of girls (aged 5-7 years) in The Guide Association

rainbow

American  

[reyn-boh] / ˈreɪnˌboʊ /

noun

1. a bow or arc of prismatic colors appearing in the heavens opposite the sun and caused by the refraction and reflection of the sun's rays in drops of rain.

2. a similar bow of colors, especially one appearing in the spray of a waterfall or fountain.

3. any brightly multicolored arrangement or display.

4. a wide variety or range; gamut.

5. a visionary goal.

   He pursued the rainbow of a singing career for years before becoming a success.

6. rainbow trout.

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adjective

1. having a diverse membership; including representatives from different races, ethnicities, genders, sexual orientations, etc.: LGBTQ Pride month celebrates all of the rainbow community.

   Archbishop Desmond Tutu famously described postapartheid South Africa as a rainbow nation.

   LGBTQ Pride month celebrates all of the rainbow community.

   Candidates are appealing to a rainbow coalition of minority voters.

rainbow ¹ British  

/ ˈreɪnˌbəʊ /

noun

1. a bow-shaped display in the sky of the colours of the spectrum, caused by the refraction and reflection of the sun's rays through rain or mist

2. 1. any similar display of bright colours

   2. ( as modifier )

      a rainbow pattern

3. an illusory hope

   to chase rainbows

4. (modifier) of or relating to a political grouping together by several minorities, esp of different races

   the rainbow coalition

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Rainbow ² British  

/ ˈreɪnˌbəʊ /

noun

1. a member of the Rainbow Guides, the youngest group of girls (aged 5-7 years) in The Guide Association

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rainbow Scientific  

/ rān′bō′ /

1. An arc-shaped spectrum of color seen in the sky opposite the Sun, especially after rain, caused by the refraction and reflection of sunlight by droplets of water suspended in the air. Secondary rainbows that are larger and paler sometimes appear within the primary arc with the colors reversed (red being inside). These result from two reflections and refractions of a light ray inside a droplet.

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rainbow Cultural  

1. The colored arch in the sky that is often seen after a rain. The rainbow is formed when water droplets in the air cause the diffraction of sunlight.

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Discover More

The colors of the rainbow are violet, indigo, blue, green, yellow, orange, and red.

Other Word Forms

• rainbowlike
  adjective
• rainbowy
  adjective

Etymology

Origin of rainbow

First recorded before 1000; Middle English reinbowe, Old English regnboga, rēnboga; cognate with Old Norse regnbogi, German Regenbogen; see rain, bow ²

Explanation

That colorful arc you sometimes see in the sky right after it stops raining? That's a rainbow. The scientific explanation for a rainbow's appearance is that light is refracted in water droplets, briefly revealing the full visible spectrum of light — all of the colors that make it up. While there are actually about a hundred colors in the visible spectrum, we tend to describe a rainbow as having six or seven. In Old English, there were two words for this phenomenon: scurboga, or "shower-bow," proved to be less popular than renboga, "rain bow."

Example Sentences

This process creates a spectrum, which is similar to a rainbow that reveals how light is distributed across different wavelengths.

From Science Daily • May 5, 2026

From there we can make an easy upward sweep to the rainbow.

From The Wall Street Journal • May 1, 2026

On a flight, listening to a song Shubham liked, she looked out of the window and saw a rainbow.

From BBC • Apr. 21, 2026

According to the Washington Litigation Group, which initiated legal proceedings in New York to demand the return of the rainbow colors, the administration agreed, under a settlement, to reinstall the flag permanently.

From Barron's • Apr. 13, 2026

“Two species of Hemiptera, or ‘true bugs’—Neacoryphus rubicollis AND Piesma brachiale—plus the leg of a rainbow grasshopper, all of which are endemic to the western United States, not Ohio.”

From "The Smartest Kid in the Universe" by Chris Grabenstein