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

The waxing gibbous moon dances with the large, gaseous Jupiter on the evening of June 23 in the southeast. Blaine Friedlander, Washington Post, "Space nerds, mark your calendar — Astronomy night on the Mall is Saturday," 20 June 2018 About one-quarter up from the horizon to the point overhead will be a waxing gibbous moon, illuminated 93 percent by the sun. Joe Rao,, "The Moon Has a Close Encounter with Saturn on Tuesday Night," 23 July 2018 The waxing gibbous moon approaches Mars on July 26 but appears to loiter near the planet the next day. Blaine P. Friedlander Jr., Washington Post, "Skywatch: July is the month of Mars," 30 June 2018 This Thursday, the moon will be in the final moments of its first quarter phase before transitioning to a waxing gibbous on Friday., "Don't Sleep On The Summer Solstice Moon," 19 June 2018 See the waxing gibbous moon scoot by the gaseous Jupiter on June 23 as the planet sets in the western sky before dawn now. Blaine P. Friedlander Jr., Washington Post, "Skywatch: Saturn, Jupiter and Mars heading for opposition in June and July," 2 June 2018 Moon Meets Mars—June 3 Mars will rise around local midnight in the early part of the month, and on June 3, early risers looking toward the southeast will be able to see the red planet pair up with the waning gibbous moon. National Geographic, "Naked-Eye Asteroid and More Can't-Miss Sky Events in June," 1 June 2018 Catch the gibbous moon approaching Saturn, which is at zero magnitude, bright, starting around June 26. Blaine P. Friedlander Jr., Washington Post, "Skywatch: Saturn, Jupiter and Mars heading for opposition in June and July," 2 June 2018 From June 22 to 24, watch as the gibbous moon pays a visit to Jupiter about halfway up the southern sky after your local nightfall. National Geographic, "Naked-Eye Asteroid and More Can't-Miss Sky Events in June," 1 June 2018

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

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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

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