A person who engages in the act of flipping another person the bird while driving on a roadway where they can not be stopped or caught, thus, enabling you to ram THEIR finger up THEIR ass.
A portmanteau of flip and leaflet, fliflet is an all-encompassing term that can be used in the place of nearly any physical object, emotion, or state of being.
It's closest synonym is "smurf".
George: "You're acomplete, uh, fliflet!"
Sarah: "You're flifleting! I'm far less of a fliflet than Melissa."
Melissa: "Who me? I ain't no fliflet!"