Might depend on who is using the term (or who created it). The folks born planet-side might use a different term than what the space-born themselves would use.
So, if there is conflict in your story, the planet-born might use a pejorative term for the space-born. If there is no artificial gravity on their ships/stations, you could have them called 'floaters'. If they use spin to provide a bit of artificial gravity, you could have the planet-born call them 'spinners'. Or maybe their physical differences would be referenced - the 'lean', the 'weaklings'.
If it's something they call themselves, or if there's peace between all peoples, then I like paranoid marvin's 'drifters'. Maybe 'voiders'? But it might depend on who is using the term, and what is happening in the story.