Fushion
Refers to a special brand of AU Crossover in which the characters of one fandom are written into the reality of another, as it is an easy way of writing an interesting alternate universe without worldbuilding a new reality from scratch. Often, the canon characters of that reality do not make an appearance in the story and therefore fusions may not necessarily count as true crossovers.
Would you believe I've never read a Fushion fic?
(Yeah lazy sentence, stfu)