Thread:SavageOpress1138/@comment-25898954-20160816140126/@comment-3528596-20160816144250

That's a fair question. In the current policy literature, the only thing I can find is: "A crossover is defined as a story in which characters, events, settings, etc. from one fictional universe directly crossover into/enter the Star Wars universe." - Star Wars Fanon:Content policy.

I'll go snooping around some old revisions or forum threads to see if I can find anything more comprehensive. I'll hit you up with a link if I do.