A thought process that one arrives in by trying to prove or validate a statement, but in the process ends up with the original question. And now for the diagram:

To prove A, I need B, and to prove B I need C but to prove C I need A!

What is a boy to do?
I personally think that recursive thought is caused by some err in logic, such that either one identifies the mistake or goes slowly and terminally insane.

A bit more practical example. I started talking to myself. Then I stated that I was talking to myself. Then I asked myself why I was talking to myself. See: irony