In series, such as Star Trek, this is when an author attempts to gather together loose ends and dangling plotlines from every conceivable era and tie them together in a Gordian knot of retroactive continuity that, if the author is lucky, makes perfect sense and explains everything. If the author is unlucky, it usually makes the reader desire to throw the book at a convenient wall.

Some rare few authors, like Peter David, are capable of performing this feat so smoothly and successfully that you would swear the original writers had just this use in mind when they created the original material.