The act of going back in time to change an event but failing to change anything, so you go back in time again to try to change the event but fail again, causing you to go back in time again to try again, looping indefinitely.
Person 1: If you could go back in time to when you were five with all your current knowledge would you?
Person 2: Yeah, I could invest in Bitcoin early! I wouldn't have to work a day in my life!
Person 1: What if your parents didn't believe you? Then you would have to go back in time again.
Person 2: Ohh, you're right. Even if I did go back in time it wouldn't change what happens.
Person 1: It's Sisyphus' Time Machine.