Jack back flan

when you place flans on a person's back and wank onto them until you cum and then they have to eat them

Matthew pulled a Jack back flan on me last night

throw back jack

To pleasure onses self to old pictures of celebrities/porn stars who are currently past there prime.

"She may be ugly now, but I keep some of her old pictures from the 90s for a throw back jack"

Jack Back

He's basically David Guetta in a nickname

Dude: Do you listen to Jack Back
Another Dude: Who the fekfkekkf is that?

Dude: Bro it's David Guetta!

Another Dude: OOOOOOOOOOHHHHHHH!!!