The term 'gaseous envelope' refers to a layer of gas surrounding a planet or celestial body. There are several other related terms that can be used interchangeably to describe this phenomenon. One possible synonym is 'atmosphere', which describes the layer of gas that surrounds a planet and is vital to sustaining life. Another term, 'aerosphere', is used to describe the uppermost region of the atmosphere, closest to space. Finally, 'exosphere' refers to the outermost part of the atmosphere, where the earth's atmosphere gradually merges with space. All of these terms are useful for describing the gaseous envelopes that surround planets, moons, and other celestial bodies in our solar system and beyond.