1
a
: marked by convexity or swelling
b
of the moon or a planet
: seen with more than half but not all of the apparent disk illuminated
2
: having a hump : humpbacked
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The adjective gibbous has its origins in the Latin noun gibbus, meaning "hump." It was adopted into Middle English to describe rounded, convex things. While it has been used to describe the rounded body parts of humans and animals (such as the back of a camel) and to describe the shape of certain flowers (such as snapdragons), the term is most often used to describe the moon: a gibbous moon is one that is between half full and full.
Examples of gibbous in a Sentence
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Saturn will rise above the eastern horizon beneath the stars of the constellation Pisces shortly before midnight for viewers in the U.S. on July 15, with the waning gibbous moon shining roughly three degrees to its upper right.
—
Anthony Wood, Space.com, 15 July 2025
Watch the waning gibbous moon, Saturn, and Neptune meet in the night sky around midnight on July 16.
—Stephanie Vermillion, Travel + Leisure, 3 July 2025
The waxing gibbous moon will shine close to the red star Antares in the constellation Scorpius on the night of June 9.
—Anthony Wood, Space.com, 8 June 2025
The waxing gibbous moon will shine close to the bright star Spica in the night sky tonight, ahead of its full moon phase on June 11.
—Anthony Wood, Space.com, 5 June 2025
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Anthony Wood, Space.com, 15 July 2025
Watch the waning gibbous moon, Saturn, and Neptune meet in the night sky around midnight on July 16.
—Stephanie Vermillion, Travel + Leisure, 3 July 2025
The waxing gibbous moon will shine close to the red star Antares in the constellation Scorpius on the night of June 9.
—Anthony Wood, Space.com, 8 June 2025
The waxing gibbous moon will shine close to the bright star Spica in the night sky tonight, ahead of its full moon phase on June 11.
—Anthony Wood, Space.com, 5 June 2025
See All Example Sentences for gibbous
Cite this Entry
“Gibbous.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/gibbous. Accessed 19 Jul. 2025.
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Medical Definition
1
: marked by swelling or convexity especially on one side : protuberant
2
: having a hump
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