With people I don't know very well, I might say that I write fiction - mostly short stories, one novel-length. Sometimes I add that I'm part of an online writers' group.
If I think they might be interested or at least open to the idea, I might get more specific. Although, these days I don't write much so the topic doesn't come up as much! I just don't feel the need to explain anything to the 'danes.
It's like, for a few years after my son was diagnosed with autism, I felt kinda compelled to bring autism into every discussion with everybody I met, but now I only mention it if it's relevant. It's a thing I do. Not everybody cares or needs to know. <shrug>
PJ