Pronunciation: [ɡˈɪbəs] (IPA) 
The word "gibbous" is spelled with a "b" and two "o's," but its pronunciation may not be immediately clear. The IPA phonetic transcription of "gibbous" is /ˈɡɪbəs/. The sound of the "b" is followed by a short "i" sound, then a long "o" sound, and another short "u" sound before the final "s." The word is often used to describe the lunar phase of the moon when it's more than half-lit but not yet full.
Gibbous is an adjective that describes the shape or phase of an object, particularly celestial bodies such as the moon. It indicates that the object appears to be more than half, but less than fully, illuminated. The term is also used to describe the bulging or protruding nature of certain shapes or features.
The primary usage of gibbous is in relation to the moon. Specifically, it refers to the moon's phase between the first quarter phase and the full moon phase. During this phase, more than half of the moon's visible Earth-facing side is illuminated, resulting in a convex or bulging shape. The word is derived from the Latin term gibbōsus, which means humpbacked or hunchbacked.
Beyond the astronomical context, gibbous can also describe other objects or structures that exhibit a similar bulging or curved shape. For instance, it can be used to depict a swelling or rounded area, as in the case of a gibbous knee. It is also employed in architecture to describe a convex or rounded design element, like a gibbous arch or doorway.
In summary, gibbous primarily refers to the phase of the moon when it appears to be more than half, but not fully, illuminated. However, it can also extend to defining other objects or structures that possess a bulging or rounded shape.
Humped, humpbacked.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.
Swelling; protuberant; in bot., swollen at the base, or having a swelling on the surface; convex, chiefly applied to the moon in her second and third quarters.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.
* The statistics data for these misspellings percentages are collected from over 15,411,110 spell check sessions on www.spellchecker.net from Jan 2010 - Jun 2012.
The word "gibbous" originated from the Latin term "gibbōsus", which means "humpbacked" or "protuberant". The term derives from the Latin noun "gibbus", meaning "hump". It was initially used in astronomy to describe the shape of the Moon or any other celestial body when it appears more than half but not fully illuminated. This term was adopted into English in the mid-17th century.
