gibbous

adjective

gib·​bous ˈji-bəs  ˈgi- 

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

Did you know?

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

Unfortunately, the bright waning gibbous moon will block all but the brightest meteors. —Stephanie Vermillion, Travel + Leisure, 1 Oct. 2025

Two nights before the full moon on the 5th, Saturn will be in a close celestial hug with a very fat gibbous moon, just two degrees to the moon’s lower left. —Mike Lynch, Twin Cities, 28 Sep. 2025

As the glowing waning gibbous moon rose over center field, the Red Sox went quietly into the night one last time in the bottom of the ninth. —Gabrielle Starr, Boston Herald, 13 Sep. 2025

Venus, Jupiter, Saturn, Neptune and Uranus are currently in the planet parade, but this weekend the waning gibbous moon joins the fray. —Jamie Carter, Forbes.com, 11 Sep. 2025

Word History

Etymology

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

First Known Use

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

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Kids Definition

gibbous

adjective

gib·​bous ˈjib-əs  ˈgib- 

: seen with more than half but not all of the disk lighted

gibbous moon

Medical Definition

gibbous

adjective

gib·​bous ˈjib-əs  ˈgib- 

1

: marked by swelling or convexity especially on one side : protuberant

2

: having a hump