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

The eight phases of the moon, in order, are: New moon Waxing crescent moon First quarter moon Waxing gibbous moon Full moon Waning gibbous moon Last quarter moon Waning crescent moon What are the names of full moons throughout the year? —Janet Loehrke, USA TODAY, 11 Feb. 2025

To Face Down Australia In Champions Trophy Semi Friday, March 7: Most Northerly Moon Tonight’s waxing gibbous moon reaches its most northerly position of the year while 64%-lit between Mars and Jupiter. —Jamie Carter, Forbes, 3 Mar. 2025

Even to a casual viewer, the waxing gibbous moon of Friday, Feb. 7 will appear unusual. —Joe Rao, Space.com, 7 Feb. 2025

At 11 days old in its lunar cycle, the moon will be in its waxing gibbous phase, with around 92% of its disk illuminated by sunlight. —Samantha Mathewson, Space.com, 10 Jan. 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