gib·​bous | \ ˈji-bəs How to pronounce gibbous (audio) , ˈgi- How to pronounce gibbous (audio) \

Definition of gibbous

1a : 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 An 82%-lit waning gibbous Moon will be between Saturn and Jupiter. Jamie Carter, Forbes, 10 July 2022 Tonight the waxing gibbous Moon will be close to Antares, the brightest star in the constellation of Scorpius. Jamie Carter, Forbes, 3 July 2022 Through binoculars or a telescope, a small gibbous appears: a mostly full Venus. Ethan Siegel, Forbes, 6 Sep. 2021 This year’s peak will take place under an unfavorable gibbous moon, but the shower should be strong enough for sky watchers to see some meteors. oregonlive, 2 Jan. 2022 The moon is unfortunately in a waxing gibbous phase on peak night, meaning that much of the moon will be visible. Megan Marples, CNN, 16 Nov. 2021 However, the waning gibbous Moon—tonight 98%-lit—will blot-out all but the very brightest bits of the great comet. Jamie Carter, Forbes, 17 Oct. 2021 According to Olson’s astronomical model, the moon on August 20, 1817 would have been in what's known as the waxing gibbous phase—when more than half of the orb is light, but it is capped with a crescent of darkness. Brigit Katz, Smithsonian, 3 July 2017 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'gibbous.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of gibbous

14th century, in the meaning defined at sense 1a

History and Etymology for gibbous

Middle English, from Late Latin gibbosus humpbacked, from Latin gibbus hump

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Last Updated

20 Jul 2022

Cite this Entry

“Gibbous.” Dictionary, Merriam-Webster, Accessed 21 Jul. 2022.

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More Definitions for gibbous


gib·​bous | \ ˈjib-əs How to pronounce gibbous (audio) , ˈgib- How to pronounce gibbous (audio) \

Medical Definition of gibbous

1 : marked by swelling or convexity especially on one side : protuberant
2 : having a hump


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