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

What to know about lunar phase As of March 6, the moon is over 90% full and in a waning gibbous phase after a full moon, as per the Old Farmer's Almanac. —Jordan Green, Memphis Commercial Appeal, 6 Mar. 2026

As of March 5, the moon is more than 90% full and in a waning gibbous phase following a full moon, according to the Old Farmer's Almanac. —Eric Lagatta, AZCentral.com, 5 Mar. 2026

However, this year, the Orionids peak under a bright waxing gibbous moon, which will wash out many fainter meteors. —Michele Laufik, Martha Stewart, 3 Mar. 2026

Jupiter, meanwhile, will shine high in the eastern sky, with the waxing gibbous moon below, obscuring the stars of the constellation Cancer with its reflected light. —Anthony Wood, Space.com, 26 Feb. 2026

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