rabbit hole
noun
University
1
A bizarre world, where everyday rules do not apply.
2
A way into such a world.
3
A time-consuming tangent or detour, often one from which it is difficult to extricate oneself.
4
The initial clue that leads to an alternate reality game.
5
Used other than figuratively or idiomatically: see rabbit, hole. The entrance to a rabbit warren or burrow; the whole warren or burrow.