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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Did You Know?

The adjective "gibbous" has its origins in the Latin noun gibbus, meaning "hump," and in the Late Latin adjective gibbosus, meaning "humpbacked," which Middle English adopted in the 14th century as "gibbous." "Gibbous" has been used to describe the rounded body parts of humans and animals (such as the back of a hunchback or camel) or to describe the shape of certain flowers (such as snapdragons). The term is most often identified, however, with the study of astronomy. In fact, if you run across the word gibbous, chances are you'll find the word moon somewhere nearby. A gibbous moon is one that is more than a half-moon but less than full.

Examples of gibbous in a Sentence

Recent Examples on the Web Things are looking good: The sun and a waning gibbous moon compete for attention in a nearly cloudless sky, and an aerostat tethered close to the pad registers almost no wind. Daniel Oberhaus, Wired, "Giant Surveillance Balloons Are Lurking at the Edge of Space," 19 Dec. 2019 This week in the night sky Moon buzzes the Beehive: After dark on Saturday, look in the eastern sky for the waning gibbous moon, which will act as a guidepost to hunt down the bright Beehive star cluster in the constellation Cancer, the crab. National Geographic, "Is the sun getting stranger?," 11 Dec. 2019 The waxing gibbous moon will act as a convenient guidepost. National Geographic, "Should we sacrifice our skies for 5G service?," 4 Dec. 2019 People with even the smallest backyard telescopes will be able to see both planets as distinct disks; Jupiter will showcase its brown cloud belts, while Venus will appear as a miniature version of a gibbous moon. Keith Ladzinski, National Geographic, "Will rising seas claim Nasa's Kennedy Space Center?," 20 Nov. 2019 Unfortunately for star gazers and meteor shower fans, a waning gibbous moon will light up the sky during the shower’s peak night. oregonlive, "Will you be able to watch the Leonid meteor shower? Peak viewing time, forecast," 14 Nov. 2019 The moon is in its waning gibbous phase about halfway lit, meaning that seeing the meteors won’t be as easy as the dark skies of a new moon, which doesn’t happen until Oct. 28. Richard Tribou,, "2019 Orionid meteor shower to peak early Tuesday," 21 Oct. 2019 This weekend the waxing gibbous moon will be passing by the bright planet Saturn just above the constellation Sagittarius. Mike Lynch, Twin Cities, "Mike Lynch: Celestial congestion of Hercules Cluster is a treasure," 8 Sep. 2019 Moon and Saturn—September 7 Look towards the southern sky at dusk for the waxing gibbous moon paying a visit with Saturn. Andrew Fazekas, National Geographic, "See Neptune at its best and more top stargazing in September," 1 Sep. 2019

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.

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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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Time Traveler for gibbous

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The first known use of gibbous was in the 14th century

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Last Updated

27 Dec 2019

Cite this Entry

“Gibbous.” The Dictionary, Merriam-Webster Inc., Accessed 28 January 2020.

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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 : humpbacked

Comments on gibbous

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showing steady, earnest care and effort

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