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

For North America, the current spectacular series began Nov. 16, when the Pleiades disappeared at the bright edge and reappeared from behind the dark edge of a waning gibbous moon. —Joe Rao, Space.com, 9 Jan. 2025

Related: Meteor showers: When is the next one? Jan. 9: The moon hides the Pleiades — A waxing gibbous moon crosses in front of this famous open cluster of stars during the early evening hours. —Joe Rao, Space.com, 31 Dec. 2024

The observing conditions this year will be reasonably good, with a waning gibbous moon not rising until midnight. —Jamie Carter, Forbes, 19 Dec. 2024

This year, the shower coincides with a waning gibbous moon, which will rise around 11:15 p.m. (ET and PT), according to Time and Date. —Raja Krishnamoorthi, Newsweek, 16 Dec. 2024

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