Guardian, "conworlding" is a term used by people who world-build for it's own sake. It's completely synonymous, but people who conlang (contruct languages) use the term because it's analogous to conlanging.
I'm going to add my confusion to the pile. Building a new world is still conworlding. You just have a lot of different conworlds involved.
I have one world (my first) where I have forty or fifty novels worth of ideas.
But! I don't just want to write high/epic fantasy set in that world. I want to write New Weird, and Urban Fantasy, and Chimney-punk, and Space Opera, and Science-fantasy, and steampunk, and cyberpunk, and postcyberpunk (which I only call it because people keep telling me cyberpunk is dead. Lies!) and hard SF, and near-future SF, and soft SF, and secondary-world contemp fiction, and secondary-world historical fiction. And I want to have different characters, and different cultures, and different time periods.