ガス巨きょ星せいMeanings1noungas giantastronomy›Astronomical term for a large planet composed mainly of hydrogen and helium, such as Jupiter or Saturn. Often used in contrast to 岩石惑星 (rocky planets).See also: 巨大ガス惑星木もく星せいは太たい陽よう系けい最さい大だいのガス巨きょ星せいです。Jupiter is the largest gas giant in the solar system.ガス巨きょ