All things written speculative fiction - books, short stories, poems, etc. As always, please tag spoilers and follow the instance rules.
Speculative fiction encompasses more than just what we consider "science fiction". It is basically just a blanket term to mean stories that happen outside of our known universe. It can be futuristic, supernatural, etc. It doesn't refer to a specific genre, but can encompass multiple subgenres.
Hope that helps!
Thanks! This seems like a very broad but workable definition. Would you say all sci-fi is speculative fiction?
Great question! I wish I could give you a satisfying binary yes or no answer, but unfortunately like most of our world, it just depends. I would say most sci-fi could be considered speculative fiction, but there might be exceptions. I found this cool chart that I think might help out. 
Safe to say most sci-fi is considered speculative though!
Source: https://annieneugebauer.com/2014/03/24/what-is-speculative-fiction/
I live Venn diagrams! Thanks for sharing this!
Speculative fiction is for people who don't want to admit they read science fiction. In the same way some people read graphic novels not comics (especially if they are collections of comic books) and go to see elevated horror but none of that ordinary stuff. Heaven forfend they get their cultural shoes mucky down here with the rest of us plebs.