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

That technically places it above the +6 detection limit of the human eye in perfect dark sky conditions, though the light cast by the waning gibbous moon will add an extra barrier to visibility in the week ahead. —Anthony Wood, Space.com, 10 Oct. 2025

In between these two extremes our planet will appear as a crescent or half full or gibbous (between half and full) over the course of that orbit. —Phil Plait, Scientific American, 9 Oct. 2025

According to EarthSky, a waning gibbous moon will be lighting up the sky around the time of the peak. —Rachael O'Connor, MSNBC Newsweek, 6 Oct. 2025

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