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
Recent Examples on the Web
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
Later, August will bring the Perseid meteor shower, though a bright waning gibbous moon might overshadow the show.
—Racquel Bazos, Baltimore Sun, 1 June 2025
Those under clear, dark skies away from light pollution may see the glow of the aurora borealis low on the northern horizon from northern U.S. states, with a waning gibbous moon rising well after midnight making conditions ideal.
—Jamie Carter, Forbes.com, 16 May 2025
On May 13, bright Antares will rise to the left of the waning gibbous moon in the southeastern sky, with just a few degrees of separation between the two celestial bodies.
—Anthony Wood, Space.com, 13 May 2025
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Anthony Wood, Space.com, 5 June 2025
Later, August will bring the Perseid meteor shower, though a bright waning gibbous moon might overshadow the show.
—Racquel Bazos, Baltimore Sun, 1 June 2025
Those under clear, dark skies away from light pollution may see the glow of the aurora borealis low on the northern horizon from northern U.S. states, with a waning gibbous moon rising well after midnight making conditions ideal.
—Jamie Carter, Forbes.com, 16 May 2025
On May 13, bright Antares will rise to the left of the waning gibbous moon in the southeastern sky, with just a few degrees of separation between the two celestial bodies.
—Anthony Wood, Space.com, 13 May 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 13 Jun. 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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