Shortcut
Also said as Looping level design, Loop back, One-way door
A door, lift or ladder that links a far part of the level back to an earlier one, usually opened from the far side. Looping level design builds the whole map around these, so the level folds back on itself.
It turns the place you just fought through into a route you now own, and cuts the walk after every death. Finding one is a reward that costs the designer no new art at all.
Say it
“The run back to the boss takes three minutes. Add a door in the boss antechamber that only opens from that side and leads to the first bonfire.”
Where you’ve seen it
Dark Souls is famous for it: the lift at the Undead Parish drops you back down to Firelink Shrine, hours of winding route later, and suddenly the map in your head joins up.
Not to be confused with fast travel
Fast travel skips the world through a menu. A shortcut is a piece of the world, and finding it changes how you picture the map.